hypothesis vs scientific theory

Hypothesis vs. Theory

A hypothesis is either a suggested explanation for an observable phenomenon, or a reasoned prediction of a possible causal correlation among multiple phenomena. In science , a theory is a tested, well-substantiated, unifying explanation for a set of verified, proven factors. A theory is always backed by evidence; a hypothesis is only a suggested possible outcome, and is testable and falsifiable.

Comparison chart

Examples of Theory and Hypothesis

Theory: Einstein's theory of relativity is a theory because it has been tested and verified innumerable times, with results consistently verifying Einstein's conclusion. However, simply because Einstein's conclusion has become a theory does not mean testing of this theory has stopped; all science is ongoing. See also the Big Bang theory , germ theory , and climate change .

Hypothesis: One might think that a prisoner who learns a work skill while in prison will be less likely to commit a crime when released. This is a hypothesis, an "educated guess." The scientific method can be used to test this hypothesis, to either prove it is false or prove that it warrants further study. (Note: Simply because a hypothesis is not found to be false does not mean it is true all or even most of the time. If it is consistently true after considerable time and research, it may be on its way to becoming a theory.)

This video further explains the difference between a theory and a hypothesis:

Common Misconception

People often tend to say "theory" when what they're actually talking about is a hypothesis. For instance, "Migraines are caused by drinking coffee after 2 p.m. — well, it's just a theory, not a rule."

This is actually a logically reasoned proposal based on an observation — say 2 instances of drinking coffee after 2 p.m. caused a migraine — but even if this were true, the migraine could have actually been caused by some other factors.

Because this observation is merely a reasoned possibility, it is testable and can be falsified — which makes it a hypothesis, not a theory.

• What is a Scientific Hypothesis? - LiveScience
• Wikipedia:Scientific theory

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Comments: Hypothesis vs Theory

Anonymous comments (2).

October 11, 2013, 1:11pm "In science, a theory is a well-substantiated, unifying explanation for a set of verified, proven hypotheses." But there's no such thing as "proven hypotheses". Hypotheses can be tested/falsified, they can't be "proven". That's just not how science works. Logical deductions based on axioms can be proven, but not scientific hypotheses. On top of that I find it somewhat strange to claim that a theory doesn't have to be testable, if it's built up from hypotheses, which DO have to be testable... — 80.✗.✗.139

May 6, 2014, 11:45pm "Evolution is a theory, not a fact, regarding the origin of living things." this statement is poorly formed because it implies that a thing is a theory until it gets proven and then it is somehow promoted to fact. this is just a misunderstanding of what the words mean, and of how science progresses generally. to say that a theory is inherently dubious because "it isn't a fact" is pretty much a meaningless statement. no expression which qualified as a mere fact could do a very good job of explaining the complicated process by which species have arisen on Earth over the last billion years. in fact, if you claimed that you could come up with such a single fact, now THAT would be dubious! everything we observe in nature supports the theory of evolution, and nothing we observe contradicts it. when you can say this about a theory, it's a pretty fair bet that the theory is correct. — 71.✗.✗.151

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This is the Difference Between a Hypothesis and a Theory

What to Know A hypothesis is an assumption made before any research has been done. It is formed so that it can be tested to see if it might be true. A theory is a principle formed to explain the things already shown in data. Because of the rigors of experiment and control, it is much more likely that a theory will be true than a hypothesis.

As anyone who has worked in a laboratory or out in the field can tell you, science is about process: that of observing, making inferences about those observations, and then performing tests to see if the truth value of those inferences holds up. The scientific method is designed to be a rigorous procedure for acquiring knowledge about the world around us.

In scientific reasoning, a hypothesis is constructed before any applicable research has been done. A theory, on the other hand, is supported by evidence: it's a principle formed as an attempt to explain things that have already been substantiated by data.

Toward that end, science employs a particular vocabulary for describing how ideas are proposed, tested, and supported or disproven. And that's where we see the difference between a hypothesis and a theory .

A hypothesis is an assumption, something proposed for the sake of argument so that it can be tested to see if it might be true.

In the scientific method, the hypothesis is constructed before any applicable research has been done, apart from a basic background review. You ask a question, read up on what has been studied before, and then form a hypothesis.

What is a Hypothesis?

A hypothesis is usually tentative, an assumption or suggestion made strictly for the objective of being tested.

When a character which has been lost in a breed, reappears after a great number of generations, the most probable hypothesis is, not that the offspring suddenly takes after an ancestor some hundred generations distant, but that in each successive generation there has been a tendency to reproduce the character in question, which at last, under unknown favourable conditions, gains an ascendancy. Charles Darwin, On the Origin of Species , 1859 According to one widely reported hypothesis , cell-phone transmissions were disrupting the bees' navigational abilities. (Few experts took the cell-phone conjecture seriously; as one scientist said to me, "If that were the case, Dave Hackenberg's hives would have been dead a long time ago.") Elizabeth Kolbert, The New Yorker , 6 Aug. 2007

What is a Theory?

A theory , in contrast, is a principle that has been formed as an attempt to explain things that have already been substantiated by data. It is used in the names of a number of principles accepted in the scientific community, such as the Big Bang Theory . Because of the rigors of experimentation and control, its likelihood as truth is much higher than that of a hypothesis.

It is evident, on our theory , that coasts merely fringed by reefs cannot have subsided to any perceptible amount; and therefore they must, since the growth of their corals, either have remained stationary or have been upheaved. Now, it is remarkable how generally it can be shown, by the presence of upraised organic remains, that the fringed islands have been elevated: and so far, this is indirect evidence in favour of our theory . Charles Darwin, The Voyage of the Beagle , 1839 An example of a fundamental principle in physics, first proposed by Galileo in 1632 and extended by Einstein in 1905, is the following: All observers traveling at constant velocity relative to one another, should witness identical laws of nature. From this principle, Einstein derived his theory of special relativity. Alan Lightman, Harper's , December 2011

Non-Scientific Use

In non-scientific use, however, hypothesis and theory are often used interchangeably to mean simply an idea, speculation, or hunch (though theory is more common in this regard):

The theory of the teacher with all these immigrant kids was that if you spoke English loudly enough they would eventually understand. E. L. Doctorow, Loon Lake , 1979 Chicago is famous for asking questions for which there can be no boilerplate answers. Example: given the probability that the federal tax code, nondairy creamer, Dennis Rodman and the art of mime all came from outer space, name something else that has extraterrestrial origins and defend your hypothesis . John McCormick, Newsweek , 5 Apr. 1999 In his mind's eye, Miller saw his case suddenly taking form: Richard Bailey had Helen Brach killed because she was threatening to sue him over the horses she had purchased. It was, he realized, only a theory , but it was one he felt certain he could, in time, prove. Full of urgency, a man with a mission now that he had a hypothesis to guide him, he issued new orders to his troops: Find out everything you can about Richard Bailey and his crowd. Howard Blum, Vanity Fair , January 1995

And sometimes one term is used as a genus, or a means for defining the other:

Laplace's popular version of his astronomy, the Système du monde , was famous for introducing what came to be known as the nebular hypothesis , the theory that the solar system was formed by the condensation, through gradual cooling, of the gaseous atmosphere (the nebulae) surrounding the sun. Louis Menand, The Metaphysical Club , 2001 Researchers use this information to support the gateway drug theory — the hypothesis that using one intoxicating substance leads to future use of another. Jordy Byrd, The Pacific Northwest Inlander , 6 May 2015 Fox, the business and economics columnist for Time magazine, tells the story of the professors who enabled those abuses under the banner of the financial theory known as the efficient market hypothesis . Paul Krugman, The New York Times Book Review , 9 Aug. 2009

Incorrect Interpretations of "Theory"

Since this casual use does away with the distinctions upheld by the scientific community, hypothesis and theory are prone to being wrongly interpreted even when they are encountered in scientific contexts—or at least, contexts that allude to scientific study without making the critical distinction that scientists employ when weighing hypotheses and theories.

The most common occurrence is when theory is interpreted—and sometimes even gleefully seized upon—to mean something having less truth value than other scientific principles. (The word law applies to principles so firmly established that they are almost never questioned, such as the law of gravity.)

This mistake is one of projection: since we use theory in general use to mean something lightly speculated, then it's implied that scientists must be talking about the same level of uncertainty when they use theory to refer to their well-tested and reasoned principles.

The distinction has come to the forefront particularly on occasions when the content of science curricula in schools has been challenged—notably, when a school board in Georgia put stickers on textbooks stating that evolution was "a theory, not a fact, regarding the origin of living things." As Kenneth R. Miller, a cell biologist at Brown University, has said , a theory "doesn’t mean a hunch or a guess. A theory is a system of explanations that ties together a whole bunch of facts. It not only explains those facts, but predicts what you ought to find from other observations and experiments.”

While theories are never completely infallible, they form the basis of scientific reasoning because, as Miller said "to the best of our ability, we’ve tested them, and they’ve held up."

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Scientific Theory Definition and Examples

A scientific theory is a well-established explanation of some aspect of the natural world. Theories come from scientific data and multiple experiments. While it is not possible to prove a theory, a single contrary result using the scientific method can disprove it. In other words, a theory is testable and falsifiable.

Examples of Scientific Theories

There are many scientific theory in different disciplines:

• Astronomy : theory of stellar nucleosynthesis , theory of stellar evolution
• Biology : cell theory, theory of evolution, germ theory, dual inheritance theory
• Chemistry : atomic theory, Bronsted Lowry acid-base theory , kinetic molecular theory of gases , Lewis acid-base theory , molecular theory, valence bond theory
• Geology : climate change theory, plate tectonics theory
• Physics : Big Bang theory, perturbation theory, theory of relativity, quantum field theory

Criteria for a Theory

In order for an explanation of the natural world to be a theory, it meets certain criteria:

• A theory is falsifiable. At some point, a theory withstands testing and experimentation using the scientific method.
• A theory is supported by lots of independent evidence.
• A theory explains existing experimental results and predicts outcomes of new experiments at least as well as other theories.

Difference Between a Scientific Theory and Theory

Usually, a scientific theory is just called a theory. However, a theory in science means something different from the way most people use the word. For example, if frogs rain down from the sky, a person might observe the frogs and say, “I have a theory about why that happened.” While that theory might be an explanation, it is not based on multiple observations and experiments. It might not be testable and falsifiable. It’s not a scientific theory (although it could eventually become one).

Value of Disproven Theories

Even though some theories are incorrect, they often retain value.

For example, Arrhenius acid-base theory does not explain the behavior of chemicals lacking hydrogen that behave as acids. The Bronsted Lowry and Lewis theories do a better job of explaining this behavior. Yet, the Arrhenius theory predicts the behavior of most acids and is easier for people to understand.

Another example is the theory of Newtonian mechanics. The theory of relativity is much more inclusive than Newtonian mechanics, which breaks down in certain frames of reference or at speeds close to the speed of light . But, Newtonian mechanics is much simpler to understand and its equations apply to everyday behavior.

Difference Between a Scientific Theory and a Scientific Law

The scientific method leads to the formulation of both scientific theories and laws . Both theories and laws are falsifiable. Both theories and laws help with making predictions about the natural world. However, there is a key difference.

A theory explains why or how something works, while a law describes what happens without explaining it. Often, you see laws written in the form of equations or formulas.

Theories and laws are related, but theories never become laws or vice versa.

Theory vs Hypothesis

A hypothesis is a proposition that is tested via an experiment. A theory results from many, many tested hypotheses.

Theory vs Fact

Theories depend on facts, but the two words mean different things. A fact is an irrefutable piece of evidence or data. Facts never change. A theory, on the other hand, may be modified or disproven.

Difference Between a Theory and a Model

Both theories and models allow a scientist to form a hypothesis and make predictions about future outcomes. However, a theory both describes and explains, while a model only describes. For example, a model of the solar system shows the arrangement of planets and asteroids in a plane around the Sun, but it does not explain how or why they got into their positions.

• Frigg, Roman (2006). “ Scientific Representation and the Semantic View of Theories .”  Theoria . 55 (2): 183–206. 
• Halvorson, Hans (2012). “What Scientific Theories Could Not Be.”  Philosophy of Science . 79 (2): 183–206. doi: 10.1086/664745
• McComas, William F. (December 30, 2013).  The Language of Science Education: An Expanded Glossary of Key Terms and Concepts in Science Teaching and Learning . Springer Science & Business Media. ISBN 978-94-6209-497-0.
• National Academy of Sciences (US) (1999). Science and Creationism: A View from the National Academy of Sciences (2nd ed.). National Academies Press. doi: 10.17226/6024  ISBN 978-0-309-06406-4. 
• Suppe, Frederick (1998). “Understanding Scientific Theories: An Assessment of Developments, 1969–1998.”  Philosophy of Science . 67: S102–S115. doi: 10.1086/392812

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Biology archive

Course: biology archive   >   unit 1, the scientific method.

• Controlled experiments
• The scientific method and experimental design

Introduction

• Make an observation.
• Ask a question.
• Form a hypothesis , or testable explanation.
• Make a prediction based on the hypothesis.
• Test the prediction.
• Iterate: use the results to make new hypotheses or predictions.

Scientific method example: Failure to toast

1. make an observation., 2. ask a question., 3. propose a hypothesis., 4. make predictions., 5. test the predictions..

• If the toaster does toast, then the hypothesis is supported—likely correct.
• If the toaster doesn't toast, then the hypothesis is not supported—likely wrong.

Logical possibility

Practical possibility, building a body of evidence, 6. iterate..

• If the hypothesis was supported, we might do additional tests to confirm it, or revise it to be more specific. For instance, we might investigate why the outlet is broken.
• If the hypothesis was not supported, we would come up with a new hypothesis. For instance, the next hypothesis might be that there's a broken wire in the toaster.

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Discussion with Kara Rogers of how the scientific model is used to test a hypothesis or represent a theory

“Theory” vs. “Hypothesis”: What Is The Difference?

Chances are you’ve heard of the TV show The Big Bang Theory . Lots of people love this lighthearted sitcom for its quirky characters and their relationships, but others haven’t even given the series a chance for one reason: they don’t like science and assume the show is boring.

However, it only takes a few seconds with Sheldon and Penny to disprove this assumption and realize that this theory ab0ut The Big Bang Theory is wrong—it isn’t a scientific snoozefest.

But wait: is it a theory or a  hypothesis about the show that leads people astray? And would the actual big bang theory— the one that refers to the beginning of the universe—mean the same thing as a big bang hypothesis ?

Let’s take a closer look at theory and hypothesis to nail down what they mean.

What does theory mean?

As a noun, a theory is a group of tested general propositions “commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena .” This is what is known as a scientific   theory , which by definition is “an understanding that is based on already tested data or results .” Einstein’s theory of relativity and the  theory of evolution are both examples of such tested propositions .

Theory is also defined as a proposed explanation you might make about your own life and observations, and it’s one “whose status is still conjectural and subject to experimentation .” For example:  I’ve got my own theories about why he’s missing his deadlines all the time.  This example refers to an idea that has not yet been proven.

There are other uses of the word theory as well.

• In this example,  theory is “a body of principles or theorems belonging to one subject.” It can be a branch of science or art that deals with its principles or methods .
• For example: when she started to follow a new parenting theory based on a trendy book, it caused a conflict with her mother, who kept offering differing opinions .

First recorded in 1590–1600, theory originates from the Late Latin theōria , which stems from the Greek theōría. Synonyms for theory include approach , assumption , doctrine , ideology , method , philosophy , speculation , thesis , and understanding .

What does hypothesis mean?

Hypothesis is a noun that means “a proposition , or set of propositions, set forth as an explanation” that describe “some specified group of phenomena.” Sounds familiar to theory , no?

But, unlike a theory , a scientific  hypothesis is made before testing is done and isn’t based on results. Instead, it is the basis for further investigation . For example: her working hypothesis is that this new drug also has an unintended effect on the heart, and she is curious what the clinical trials  will show .

Hypothesis also refers to “a proposition assumed as a premise in an argument,” or “mere assumption or guess.” For example:

• She decided to drink more water for a week to test out her hypothesis that dehydration was causing her terrible headaches.
• After a night of her spouse’s maddening snoring, she came up with the hypothesis that sleeping on his back was exacerbating the problem.

Hypothesis was first recorded around 1590–1600 and originates from the Greek word hypóthesis (“basis, supposition”). Synonyms for hypothesis include: assumption , conclusion , conjecture , guess , inference , premise , theorem , and thesis .

How to use each

Although theory in terms of science is used to express something based on extensive research and experimentation, typically in everyday life, theory is used more casually to express an educated guess.

So in casual language,  theory and hypothesis are more likely to be used interchangeably to express an idea or speculation .

In most everyday uses, theory and hypothesis convey the same meaning. For example:

• Her opinion is just a theory , of course. She’s just guessing.
• Her opinion is just a hypothesis , of course. She’s just guessing.

It’s important to remember that a scientific   theory is different. It is based on tested results that support or substantiate it, whereas a hypothesis is formed before the research.

For example:

• His  hypothesis  for the class science project is that this brand of plant food is better than the rest for helping grass grow.
• After testing his hypothesis , he developed a new theory based on the experiment results: plant food B is actually more effective than plant food A in helping grass grow.

In these examples, theory “doesn’t mean a hunch or a guess,” according to Kenneth R. Miller, a cell biologist at Brown University. “A theory is a system of explanations that ties together a whole bunch of facts. It not only explains those facts, but predicts what you ought to find from other observations and experiments.”

So if you have a concept that is based on substantiated research, it’s a theory .

But if you’re working off of an assumption that you still need to test, it’s a hypothesis .

So remember, first comes a hypothesis , then comes theory . Now who’s ready for a  Big Bang Theory marathon?

Now that you’ve theorized and hypothesized through this whole article … keep testing your judgment (Or is it judgement?). Find out the correct spelling here!

Or find out the difference between these two common issues below!

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What is a scientific theory?

A scientific theory is based on careful examination of facts.

• The process
• Good theory characteristics

The difference between theories, facts and laws

Additional resources, bibliography.

A scientific theory is a structured explanation to explain a group of facts or phenomena in the natural world that often incorporates a scientific hypothesis and scientific laws . The scientific definition of a theory contrasts with the definition most people use in casual language.

"The way that scientists use the word 'theory' is a little different than how it is commonly used in the lay public," said Jaime Tanner, a professor of biology at Emerson College in Boston. "Most people use the word 'theory' to mean an idea or hunch that someone has, but in science the word 'theory' refers to the way that we interpret facts."

Related: 5 sci-fi concepts that are possible (in theory)

The process of becoming a scientific theory

Every scientific theory relies on the scientific method . A scientist may make an observation and devise a hypothesis to explain that observation, then design an experiment to test that hypothesis. If the hypothesis is shown to be incorrect, the scientist will develop a new hypothesis and begin the process again. If the hypothesis is supported by the results of the experiment, it will go on to be tested again. If the hypothesis isn't disproven or surpassed by a better explanation, the scientist may incorporate it into a larger theory that helps to explain the observed phenomenon and relates it to other phenomena, according to the Field Museum . 

A scientific theory is not the end result of the scientific method; theories can be proven or rejected, just like hypotheses . And theories are continually improved or modified as more information is gathered, so that the accuracy of the prediction becomes greater over time.

Theories are foundations for furthering scientific knowledge and for putting the information gathered to practical use. Scientists use theories to develop inventions or find a cure for a disease.

Furthermore, a scientific theory is the framework for observations and facts, Tanner said. Theories may change, or the way that they are interpreted may change, but the facts themselves don't change. Tanner likens theories to a basket in which scientists keep facts and observations that they find. The shape of that basket may change as the scientists learn more and include more facts. "For example, we have ample evidence of traits in populations becoming more or less common over time (evolution), so evolution is a fact, but the overarching theories about evolution, the way that we think all of the facts go together might change as new observations of evolution are made," Tanner told Live Science.

Characteristics of a good theory

The University of California, Berkeley , defines a theory as "a broad, natural explanation for a wide range of phenomena. Theories are concise, coherent, systematic, predictive, and broadly applicable, often integrating and generalizing many hypotheses." 

According to Columbia University emeritus professor of philosophy Philip Kitcher, a good scientific theory has three characteristics. First, it has unity, which means it consists of a limited number of problem-solving strategies that can be applied to a wide range of scientific circumstances. Second, a good scientific theory leads to new questions and new areas of research. This means that a theory doesn't need to explain everything in order to be useful. And finally, a good theory is formed from a number of hypotheses that can be tested independently from the theory itself.

Any scientific theory must be based on a careful and rational examination of the facts. Facts and theories are two different things. In the scientific method, there is a clear distinction between facts, which can be observed and/or measured, and theories, which are scientists' explanations and interpretations of the facts. 

Some think that theories become laws, but theories and laws have separate and distinct roles in the scientific method. A law is a description of an observed phenomenon in the natural world that holds true every time it is tested. It doesn't explain why something is true; it just states that it is true. A theory, on the other hand, explains observations that are gathered during the scientific process. So, while law and theory are part of the scientific process, they are two different aspects, according to the National Center for Science Education . 

A good example of the difference between a theory and a law is the case of Gregor Mendel . In his research, Mendel discovered that two separate genetic traits would appear independently of each other in different offspring. "Yet, Mendel knew nothing of DNA or chromosomes . It wasn't until a century later that scientists discovered DNA and chromosomes — the biochemical explanation of Mendel's laws," said Peter Coppinger, an associate professor of biology and biomedical engineering at the Rose-Hulman Institute of Technology. "It was only then that scientists, such as T.H. Morgan working with fruit flies, explained the Law of Independent Assortment using the theory of chromosomal inheritance. Still today, this is the universally accepted explanation [theory] for Mendel's Law."

• When does a theory become a fact? This article from Arizona State University says you're asking the wrong question! 
• Learn the difference between the casual and scientific uses of "theory" and "law" from the cartoony stars of the Amoeba Sisters on Youtube.
• Can a scientific theory be falsified? This article from Scientific American says no. 

Kenneth Angielczyk, "What Do We Mean by "Theory" in Science?" Field Museum, March 10, 2017. https://www.fieldmuseum.org/blog/what-do-we-mean-theory-science

University of California, Berkeley, "Science at multiple levels." https://undsci.berkeley.edu/article/0_0_0/howscienceworks_19  

Philip Kitcher, "Abusing Science: The Case Against Creationism," MIT Press, 1982. 

National Center for Science Education, "Definitions of Fact, Theory, and Law in Scientific Work," March 16, 2016 https://ncse.ngo/definitions-fact-theory-and-law-scientific-work  

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How to Write a Great Hypothesis

Hypothesis Definition, Format, Examples, and Tips

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Amy Morin, LCSW, is a psychotherapist and international bestselling author. Her books, including "13 Things Mentally Strong People Don't Do," have been translated into more than 40 languages. Her TEDx talk,  "The Secret of Becoming Mentally Strong," is one of the most viewed talks of all time.

Verywell / Alex Dos Diaz

• The Scientific Method

Hypothesis Format

Falsifiability of a hypothesis.

• Operationalization

Hypothesis Types

Hypotheses examples.

• Collecting Data

A hypothesis is a tentative statement about the relationship between two or more variables. It is a specific, testable prediction about what you expect to happen in a study. It is a preliminary answer to your question that helps guide the research process.

Consider a study designed to examine the relationship between sleep deprivation and test performance. The hypothesis might be: "This study is designed to assess the hypothesis that sleep-deprived people will perform worse on a test than individuals who are not sleep-deprived."

At a Glance

A hypothesis is crucial to scientific research because it offers a clear direction for what the researchers are looking to find. This allows them to design experiments to test their predictions and add to our scientific knowledge about the world. This article explores how a hypothesis is used in psychology research, how to write a good hypothesis, and the different types of hypotheses you might use.

The Hypothesis in the Scientific Method

In the scientific method , whether it involves research in psychology, biology, or some other area, a hypothesis represents what the researchers think will happen in an experiment. The scientific method involves the following steps:

• Forming a question
• Performing background research
• Creating a hypothesis
• Designing an experiment
• Collecting data
• Analyzing the results
• Drawing conclusions
• Communicating the results

The hypothesis is a prediction, but it involves more than a guess. Most of the time, the hypothesis begins with a question which is then explored through background research. At this point, researchers then begin to develop a testable hypothesis.

Unless you are creating an exploratory study, your hypothesis should always explain what you  expect  to happen.

In a study exploring the effects of a particular drug, the hypothesis might be that researchers expect the drug to have some type of effect on the symptoms of a specific illness. In psychology, the hypothesis might focus on how a certain aspect of the environment might influence a particular behavior.

Remember, a hypothesis does not have to be correct. While the hypothesis predicts what the researchers expect to see, the goal of the research is to determine whether this guess is right or wrong. When conducting an experiment, researchers might explore numerous factors to determine which ones might contribute to the ultimate outcome.

In many cases, researchers may find that the results of an experiment  do not  support the original hypothesis. When writing up these results, the researchers might suggest other options that should be explored in future studies.

In many cases, researchers might draw a hypothesis from a specific theory or build on previous research. For example, prior research has shown that stress can impact the immune system. So a researcher might hypothesize: "People with high-stress levels will be more likely to contract a common cold after being exposed to the virus than people who have low-stress levels."

In other instances, researchers might look at commonly held beliefs or folk wisdom. "Birds of a feather flock together" is one example of folk adage that a psychologist might try to investigate. The researcher might pose a specific hypothesis that "People tend to select romantic partners who are similar to them in interests and educational level."

Elements of a Good Hypothesis

So how do you write a good hypothesis? When trying to come up with a hypothesis for your research or experiments, ask yourself the following questions:

• Is your hypothesis based on your research on a topic?
• Can your hypothesis be tested?
• Does your hypothesis include independent and dependent variables?

Before you come up with a specific hypothesis, spend some time doing background research. Once you have completed a literature review, start thinking about potential questions you still have. Pay attention to the discussion section in the  journal articles you read . Many authors will suggest questions that still need to be explored.

How to Formulate a Good Hypothesis

To form a hypothesis, you should take these steps:

• Collect as many observations about a topic or problem as you can.
• Evaluate these observations and look for possible causes of the problem.
• Create a list of possible explanations that you might want to explore.
• After you have developed some possible hypotheses, think of ways that you could confirm or disprove each hypothesis through experimentation. This is known as falsifiability.

In the scientific method ,  falsifiability is an important part of any valid hypothesis. In order to test a claim scientifically, it must be possible that the claim could be proven false.

Students sometimes confuse the idea of falsifiability with the idea that it means that something is false, which is not the case. What falsifiability means is that  if  something was false, then it is possible to demonstrate that it is false.

One of the hallmarks of pseudoscience is that it makes claims that cannot be refuted or proven false.

The Importance of Operational Definitions

A variable is a factor or element that can be changed and manipulated in ways that are observable and measurable. However, the researcher must also define how the variable will be manipulated and measured in the study.

Operational definitions are specific definitions for all relevant factors in a study. This process helps make vague or ambiguous concepts detailed and measurable.

For example, a researcher might operationally define the variable " test anxiety " as the results of a self-report measure of anxiety experienced during an exam. A "study habits" variable might be defined by the amount of studying that actually occurs as measured by time.

These precise descriptions are important because many things can be measured in various ways. Clearly defining these variables and how they are measured helps ensure that other researchers can replicate your results.

Replicability

One of the basic principles of any type of scientific research is that the results must be replicable.

Replication means repeating an experiment in the same way to produce the same results. By clearly detailing the specifics of how the variables were measured and manipulated, other researchers can better understand the results and repeat the study if needed.

Some variables are more difficult than others to define. For example, how would you operationally define a variable such as aggression ? For obvious ethical reasons, researchers cannot create a situation in which a person behaves aggressively toward others.

To measure this variable, the researcher must devise a measurement that assesses aggressive behavior without harming others. The researcher might utilize a simulated task to measure aggressiveness in this situation.

Hypothesis Checklist

• Does your hypothesis focus on something that you can actually test?
• Does your hypothesis include both an independent and dependent variable?
• Can you manipulate the variables?
• Can your hypothesis be tested without violating ethical standards?

The hypothesis you use will depend on what you are investigating and hoping to find. Some of the main types of hypotheses that you might use include:

• Simple hypothesis : This type of hypothesis suggests there is a relationship between one independent variable and one dependent variable.
• Complex hypothesis : This type suggests a relationship between three or more variables, such as two independent and dependent variables.
• Null hypothesis : This hypothesis suggests no relationship exists between two or more variables.
• Alternative hypothesis : This hypothesis states the opposite of the null hypothesis.
• Statistical hypothesis : This hypothesis uses statistical analysis to evaluate a representative population sample and then generalizes the findings to the larger group.
• Logical hypothesis : This hypothesis assumes a relationship between variables without collecting data or evidence.

A hypothesis often follows a basic format of "If {this happens} then {this will happen}." One way to structure your hypothesis is to describe what will happen to the  dependent variable  if you change the  independent variable .

The basic format might be: "If {these changes are made to a certain independent variable}, then we will observe {a change in a specific dependent variable}."

A few examples of simple hypotheses:

• "Students who eat breakfast will perform better on a math exam than students who do not eat breakfast."
• "Students who experience test anxiety before an English exam will get lower scores than students who do not experience test anxiety."​
• "Motorists who talk on the phone while driving will be more likely to make errors on a driving course than those who do not talk on the phone."
• "Children who receive a new reading intervention will have higher reading scores than students who do not receive the intervention."

Examples of a complex hypothesis include:

• "People with high-sugar diets and sedentary activity levels are more likely to develop depression."
• "Younger people who are regularly exposed to green, outdoor areas have better subjective well-being than older adults who have limited exposure to green spaces."

Examples of a null hypothesis include:

• "There is no difference in anxiety levels between people who take St. John's wort supplements and those who do not."
• "There is no difference in scores on a memory recall task between children and adults."
• "There is no difference in aggression levels between children who play first-person shooter games and those who do not."

Examples of an alternative hypothesis:

• "People who take St. John's wort supplements will have less anxiety than those who do not."
• "Adults will perform better on a memory task than children."
• "Children who play first-person shooter games will show higher levels of aggression than children who do not." 

Collecting Data on Your Hypothesis

Once a researcher has formed a testable hypothesis, the next step is to select a research design and start collecting data. The research method depends largely on exactly what they are studying. There are two basic types of research methods: descriptive research and experimental research.

Descriptive Research Methods

Descriptive research such as  case studies ,  naturalistic observations , and surveys are often used when  conducting an experiment is difficult or impossible. These methods are best used to describe different aspects of a behavior or psychological phenomenon.

Once a researcher has collected data using descriptive methods, a  correlational study  can examine how the variables are related. This research method might be used to investigate a hypothesis that is difficult to test experimentally.

Experimental Research Methods

Experimental methods  are used to demonstrate causal relationships between variables. In an experiment, the researcher systematically manipulates a variable of interest (known as the independent variable) and measures the effect on another variable (known as the dependent variable).

Unlike correlational studies, which can only be used to determine if there is a relationship between two variables, experimental methods can be used to determine the actual nature of the relationship—whether changes in one variable actually  cause  another to change.

The hypothesis is a critical part of any scientific exploration. It represents what researchers expect to find in a study or experiment. In situations where the hypothesis is unsupported by the research, the research still has value. Such research helps us better understand how different aspects of the natural world relate to one another. It also helps us develop new hypotheses that can then be tested in the future.

Thompson WH, Skau S. On the scope of scientific hypotheses .  R Soc Open Sci . 2023;10(8):230607. doi:10.1098/rsos.230607

Taran S, Adhikari NKJ, Fan E. Falsifiability in medicine: what clinicians can learn from Karl Popper [published correction appears in Intensive Care Med. 2021 Jun 17;:].  Intensive Care Med . 2021;47(9):1054-1056. doi:10.1007/s00134-021-06432-z

Eyler AA. Research Methods for Public Health . 1st ed. Springer Publishing Company; 2020. doi:10.1891/9780826182067.0004

Nosek BA, Errington TM. What is replication ?  PLoS Biol . 2020;18(3):e3000691. doi:10.1371/journal.pbio.3000691

Aggarwal R, Ranganathan P. Study designs: Part 2 - Descriptive studies .  Perspect Clin Res . 2019;10(1):34-36. doi:10.4103/picr.PICR_154_18

Nevid J. Psychology: Concepts and Applications. Wadworth, 2013.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

What Is a Hypothesis? (Science)

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A hypothesis (plural hypotheses) is a proposed explanation for an observation. The definition depends on the subject.

In science, a hypothesis is part of the scientific method. It is a prediction or explanation that is tested by an experiment. Observations and experiments may disprove a scientific hypothesis, but can never entirely prove one.

In the study of logic, a hypothesis is an if-then proposition, typically written in the form, "If X , then Y ."

In common usage, a hypothesis is simply a proposed explanation or prediction, which may or may not be tested.

Writing a Hypothesis

Most scientific hypotheses are proposed in the if-then format because it's easy to design an experiment to see whether or not a cause and effect relationship exists between the independent variable and the dependent variable . The hypothesis is written as a prediction of the outcome of the experiment.

Null Hypothesis and Alternative Hypothesis

Statistically, it's easier to show there is no relationship between two variables than to support their connection. So, scientists often propose the null hypothesis . The null hypothesis assumes changing the independent variable will have no effect on the dependent variable.

In contrast, the alternative hypothesis suggests changing the independent variable will have an effect on the dependent variable. Designing an experiment to test this hypothesis can be trickier because there are many ways to state an alternative hypothesis.

For example, consider a possible relationship between getting a good night's sleep and getting good grades. The null hypothesis might be stated: "The number of hours of sleep students get is unrelated to their grades" or "There is no correlation between hours of sleep and grades."

An experiment to test this hypothesis might involve collecting data, recording average hours of sleep for each student and grades. If a student who gets eight hours of sleep generally does better than students who get four hours of sleep or 10 hours of sleep, the hypothesis might be rejected.

But the alternative hypothesis is harder to propose and test. The most general statement would be: "The amount of sleep students get affects their grades." The hypothesis might also be stated as "If you get more sleep, your grades will improve" or "Students who get nine hours of sleep have better grades than those who get more or less sleep."

In an experiment, you can collect the same data, but the statistical analysis is less likely to give you a high confidence limit.

Usually, a scientist starts out with the null hypothesis. From there, it may be possible to propose and test an alternative hypothesis, to narrow down the relationship between the variables.

Example of a Hypothesis

Examples of a hypothesis include:

• If you drop a rock and a feather, (then) they will fall at the same rate.
• Plants need sunlight in order to live. (if sunlight, then life)
• Eating sugar gives you energy. (if sugar, then energy)
• White, Jay D.  Research in Public Administration . Conn., 1998.
• Schick, Theodore, and Lewis Vaughn.  How to Think about Weird Things: Critical Thinking for a New Age . McGraw-Hill Higher Education, 2002.
• Null Hypothesis Examples
• Examples of Independent and Dependent Variables
• Difference Between Independent and Dependent Variables
• The Difference Between Control Group and Experimental Group
• Null Hypothesis Definition and Examples
• Definition of a Hypothesis
• What Are the Elements of a Good Hypothesis?
• Six Steps of the Scientific Method
• Independent Variable Definition and Examples
• What Are Examples of a Hypothesis?
• Understanding Simple vs Controlled Experiments
• Scientific Method Flow Chart
• Scientific Method Vocabulary Terms
• What Is a Testable Hypothesis?
• What 'Fail to Reject' Means in a Hypothesis Test
• How To Design a Science Fair Experiment

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• Difference Between Hypothesis And Theory

Difference Between Theory and Hypothesis

Many of them belittle evolution because “it is just a theory.” Gravity, on the other hand, must be real because it is a law. The words “theory,” “facts,” “laws” and “hypothesis” have a very specific meaning in the scientific world that doesn’t quite match the ones we use in everyday language. A hypothesis is a tentative explanation of an observation that can be tested. It acts as a starting point for further explanation. Theory, on the other hand, is an explanation of some aspect of the natural world that’s well-justified by facts, tested hypotheses, and laws. Let us look at more differences between hypothesis and theory given in a tabular column below.

Theory vs Hypothesis

From the above differences, we can infer that a hypothesis might change significantly as the testing occurs. A hypothesis can either be right or wrong. When a hypothesis is tested and proved true, it becomes a theory. At BYJU’S, learn more differences like the difference between asteroid and comet.

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Hypothesis VS A Scientific Theory: A Comparison

A hypothesis is an explanation that is proposed for a phenomenon. If a hypothesis has to be scientific, the scientific way needs that it can be tested. Scientists basically base their hypotheses on prior observations that the available scientific theories can’t explain .

A scientific theory on the other hand, is an explanation of an aspect of the natural world or the universe which is tested and corroborated according to scientific ways. In situations where theories aren’t amenable to experimental testing, those theories will be evaluated through the principles of abductive reasoning.

One must keep in mind that even though ‘hypothesis’ and ‘theory’ are usually used interchangeably, both aren’t the same.

The difference between a hypothesis and a scientific theory is that a hypothesis is an assumption that is made prior to any research which has to be done. The hypothesis is tested in order to see if it is true or not. A theory is a principle that has to be formed in order to explain the things that are shown in data.

Here is a table for the differences between hypothesis and scientific theory:

Keep reading to know more.

Page Contents

What is a scientific theory?

A scientific theory explains an aspect of the natural world or the universe, the explanation is tested and corroborated according to the methods of science. In everyday speech, theory refers to an explanation that is a representation of an unsubstantiated and speculative guess. However, in science, the theory describes an explanation that is tested and is accepted as valid.

A scientific theory is different from a scientific fact and scientific law. A fact is merely a basic observation, while a law is a statement. Stephen Jay Gould  wrote that “Facts are the world’s data, while theories are structures of ideas which explain and interpret the facts.”

Learn the differences between fact, theory, hypothesis, and laws through this video.

A scientific theory can be rejected if it’s unfit for the new findings. Many well-established theories are unlikely to be ever changed, such as evolution and cell theory.

Scientific theories are very much testable and can form falsifiable predictions. Theories explain the cause of a certain natural phenomenon, they are also used to describe as well as predict particular aspects of the universe. Like other types of scientific knowledge, a scientific theory is deductive as well as inductive, which aims for predictive and explanatory power. Moreover, Scientists often utilize theories for further scientific information, and also to provide advancements to technology or medicine.

Furthermore, two types of scientific theories were described by Albert Einstein: “ Constructive theories” and “ Principle theories”. Constructive theories are the constructive representation of phenomena, such as kinetic theory. Principle theories, on the other hand, are empirical generalizations, for example, Newton’s laws of motion.

What is an example of a theory in science?

The world is full of theories, and some unbelievable theories are true as a theory is formed to explain the things that exist.

Here are some popular examples of theories in science:

• Big Bang Theory
• Theory of Evolution
• Quantum Field Theory
• Hubble’s Law of Cosmic Expansion
• Universal Law of Gravitation
• Newton’s Laws of Motion
• Laws of Thermodynamics
• Archimedes’ Buoyancy Principle

What does a hypothesis mean?

A hypothesis is often tentative, an assumption or suggestion that is formed strictly for the sole objective of being tested. A hypothesis is an explanation for a phenomenon. A hypothesis is based on prior observations that couldn’t be explained with the scientific theories already available.

The meaning of the adjective “hypothetical” is “Possessing the nature of a hypothesis” or “Assuming to exist as an immediate result of a hypothesis”.

People often refer to a hypothesis as an “educated guess” as it provides an outcome that is based on the evidence. Although, there are several scientists who reject the term “educated guess”. Moreover, experimenters have the right to test and reject the hypothesis prior to solving the problem.

Researchers, while weighing up alternative hypotheses, will take into consideration:

• Testability.
• Scope: The evident application of the hypothesis to several cases of phenomena.
• Fruitfulness: the likelihood of a hypothesis to explain phenomena.
• Conservatism: It’s the degree of “fit” with the existing known knowledge systems.

How do I write a hypothesis?

There are 6 steps that one has to follow to write a plausible hypothesis. Here is all the information that you would need.

• Ask a question

Curiosity has been the inspiration for many of history’s greatest scientific achievements, so the best place to begin is to ask yourself questions about the world as well as the universe. Why are things the way they are? You must choose a research topic that is interesting to you, and your curiosity will come naturally. 

• Conduct preliminary research

Gather all the background information on your research topic. How much background information you require depends on what you are attempting and what topic you chose. You might need to read several books, or it could be as simple as doing a web search to get quick answers. At this stage, you don’t necessarily need to prove or disprove your hypothesis, you merely need to gather the information that you require in order to prove or disprove it yourself. You must know first if you are right in proving or disproving this hypothesis.

• Define your variables

Once you have decided what your hypothesis will be, you will have to select variables that are independent and which are dependent. Always keep in mind that independent variables are the factors that you have absolute control over. Therefore, consider the limits of your experiment before you finalize your hypothesis. 

• Phrase it as an if-then statement

While you write your hypothesis, phrase it by using an if-then format, for example, “ If  I water a plant every day,  then  it will grow better.” This format may be tricky while dealing with multiple variables, however, generally, it’s a reliable way of expressing the cause-and-effect relationship that you’re testing. 

• Collect data to support your hypothesis

A hypothesis is a means to an end. The prime concern of any scientific research is the conclusion. Once you are done with all 4 steps, you can start with your experiments. You will be gathering data to support your hypothesis. However, if your research turns out to prove it wrong, then don’t worry, as all this is a part of the scientific method. 

• Write with confidence

Lastly, you would want a record of your findings in a research paper for other people to read. Write the research paper and be proud that you made it to the last step.

To Conclude

• The hypothesis is a tentative explanation needing scientific testing.
• Scientific Theory is backed by evidence. It is an extensively tested explanation.
• The hypothesis is untested. On the other hand, the Theory is based on existing data.
• Hypotheses need more testing. And theories encompass broad data.
• Scientific theories change, e.g., the Big Bang and the Theory of Evolution.
• The hypothesis can be defined as an “educated guess” to be tested.
• Constructing a hypothesis involves questioning, researching, defining variables, and gathering data.
• Hypotheses explain your predictions. And the theories explain natural aspects.

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Practices of Science: Opinion, Hypothesis & Theory

An opinion is a statement describing a personal belief or thought that cannot be tested (or has not been tested) and is unsupported by evidence. A hypothesis is usually a prediction based on some observation or evidence. Hypotheses must be testable, and once tested, they can be supported by evidence. If a statement is made that cannot be tested and disproved, then it is not a hypothesis. Sometimes it is possible to restate an opinion so that it can become a hypothesis.

A scientific theory is a hypothesis that has been extensively tested, evaluated by the scientific community, and is strongly supported. Theories often describe a large set of observations, and provide a cohesive explanation for those observations. An individual cannot come up with a theory. Theories require extensive testing and agreement within the scientific community. Theories are not described as true or right, but as the best-supported explanation of the world based on evidence.

SF Fig. 7.9. Alfred Wegener first proposed the idea of continental drift.

Image courtesy of Deutsches Dokumentationszentrum für Kunstgeschichte - Bildarchiv Foto Marburg, Wikimedia Commons

German-born geophysicist Alfred Wegener is credited with proposing a hypothesis of continental drift in the late 1800’s, but it was not until the 1960’s that his concept became widely accepted by the scientific community. Part of the problem Wegener faced in presenting his hypothesis of continental drift was that he did not have a sufficient evidence to be able to propose the mechanism of continental movement. Wegener suggested that the continents moved across the ocean floor, but the lack of disturbance on the ocean floor did not support this part of his hypothesis. The elevation of continental drift to the status of a theory came largely from evidence supporting new ideas about the mechanism of plate movement: plate tectonics. It was only over time, as more scientists evaluated and added to Wegener’s original hypothesis, that it became widely accepted as a theory.

• Arc-shaped island chains like the Aleutian Islands are found at subduction zones.
• Dinosaurs were mean animals.
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• The center of the earth is made of platinum.  
• You have a hypothesis that the land near your school was once at the bottom of the ocean, but due to continental movement, it is now miles inland from any water source. How would you test your hypothesis? What evidence would you use to support your claim?

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More From Forbes

New dna evidence challenges woolly mammoth extinction theory.

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How did the woolly mammoth, an ambassador of the Ice Age, end up confined to modern-day Wrangel ... [+] Island? And what ultimately caused their extinction? New evidence suggests it wasn’t poor genetics as previously thought.

Rising sea levels around 10,000 years ago transformed Wrangel Island into a final refuge for the woolly mammoths , isolating them from their mainland counterparts. As the world’s climate continued to warm and habitats changed, Wrangel Island became one of the last viable environments where these mammoths could survive, setting the stage for their final chapter.

Four millenniums ago, Wrangel Island was a frozen refuge, the last icebox where woolly mammoths ... [+] roamed, surviving long after their counterparts vanished from the mainland. This is a mammoth tusk found in the region.

A prevailing theory for the extinction of isolated populations like the woolly mammoths on Wrangel Island often points to inbreeding. Inbreeding can reduce a population’s genetic variability and increase the spread of harmful genetic mutations, leading to decreased survival and reproduction rates. A striking example is the Tasmanian tiger, or thylacine, which suffered from reduced genetic diversity due to severe inbreeding before its extinction in the 20th century.

However, this popular theory of inbreeding leading to extinction may not hold for the woolly mammoths of Wrangel Island, according to a June 2024 paper published in Cell .

There Was A ‘Bottleneck’ Event, But The Mammoth Was Well On Its Way To Recovery

The study analyzed 21 genomes from Siberian woolly mammoths and revealed that while the mammoth population did experience a significant bottleneck—an event that greatly reduces a population’s size and genetic diversity—it recovered well. In the case of the woolly mammoths on Wrangel Island, the bottleneck event occurred when rising sea levels and changing climates caused their numbers to dwindle significantly as they became isolated on the island.

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This drastic reduction in population size limited their genetic diversity and could have made them more susceptible to environmental stresses and changes.

The study found that while the Wrangel Island mammoth population began with as few as eight individuals, it grew to about 200 to 300 and remained stable until their extinction. Over time, the worst genetic mutations became less common because mammoths with these harmful traits were less likely to reproduce.

This suggests that, contrary to expectations, inbreeding did not lead to the accumulation of harmful mutations that could have caused their extinction. Instead, the isolated mammoth population was able to purge these detrimental mutations over generations, challenging the traditional view that genetic degradation was the key factor in their demise.

Did We Have Something To Do With The Extinction?

The new genetic data for woolly mammoths suggests that inbreeding was only one small part of a larger storm that was brewing. While the mammoths faced genetic challenges due to their isolation, the real threats to their survival likely came from a combination of known and unknown environmental changes and, quite possibly, human interference.

The last woolly mammoths went extinct 4,000 years ago. Around this time, human civilization was advancing technologically and expanding geographically. Early humans had reached various remote parts of the world, including areas near Wrangel Island.

This period marked significant changes in human hunting practices and land use, which could have impacted local ecosystems in profound ways. Although direct evidence of humans hunting the last mammoths on Wrangel Island is still elusive, the coinciding timelines suggest that human activity could have played a role in stressing mammoth populations, either through direct hunting or by altering their habitats.

This hypothesis aligns with broader patterns observed in other species extinctions, where human expansion and environmental impact have often been critical factors. A similar scenario unfolded with the Tasmanian tiger, which faced relentless hunting, habitat loss due to agricultural expansion and diseases introduced by invasive species. These factors combined led to its inbreeding problem and subsequent extinction.

The dodo bird is another example of extinction driven by human activity. Native to Mauritius, the dodo was unaccustomed to predators, making it vulnerable when humans arrived. The introduction of invasive species, habitat destruction and direct hunting by sailors drove the dodo to extinction by the end of the 17th century.

Once a native of Mauritius, the dodo bird met its untimely extinction due to human activities, from ... [+] habitat destruction to introduced predators, a stark reminder of the impact we have on our planet's unique creatures.

In both cases, as with the woolly mammoths, it wasn’t just one factor but a combination of human impacts and environmental changes that led to their demise. Only time will reveal the specifics of how the last woolly mammoths that roamed the earth met their end, but findings like these put things into perspective for us. They remind us that most species are resilient, built to withstand various challenges. It often takes a series of unfortunate events for a species to actually go extinct.

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