The scientific theory according to which populations change gradually through a process of natural selection.

12,530 Questions
Alligators and Crocodiles

Did crocodiles share a common ancestor with birds?

Yes. According to comparative genomics and morphology, crocodiles and birds share a common ancestor in Archosauria.


How did Hominids evolve in Africa?

The frequently-heard answer is that we moved, or were driven, from the jungle to the grasslands, losing our ape-hair in response to the heat. However, baboons, who did this, have not lost their hair, nor have any of the other grassland animals. However, a recent hypothesis suggets we had an aquatic period (other animals who have streamlined, minimised, or total loss of, body hair had or have an aquatic period - otters, seals, hippos, etc). The suggestion is that our ancestors evolved the primary human characteristics (vertical posture, etc.) as a response to living in, or habitually frequenting, water - and the target place for this origin is the Danakil Horst, at the mouth of the Red Sea.

Another perspective:

In general terms Hominids split from living apes somewhere between 5 - 10 million years ago.

They evolved from being small brained, part-time bipedal/part-time quadrupedal with fingers and hands optimized for tree climbing and lacking fully developed language processing structures in the brain (e.g.: Australopithecus Afareneis);to large brained, full-time bipedal, with hands suited to manipulating object and fully developed language processing brains structures (e.g.: Homo Erectus -> Homo Sapien).

It is thought that rapid changes in climate and survival conditions provided selective pressure that gave an advantage to Hominids that were able to quickly adapt to a variety of conditions. This drove changes that favored intelligence, tool making and language.

Regarding body hair, later bipedal hominids were hunters that ran down their prey by outlasting them. Hominids could/can run much longer distances than other animals (although not typically as fast) because bipedal running, at a jogging pace, is more energy efficient than quadrupedal running and hominids could/can cool themselves by sweating. Most "Hairy" or fur-bearing animals don't have sweat glands and those that do (Horses etc) cannot cool themselves as effectively as hairless hominids can. Loss of body hair was an adaptation to promote cooling the body temperature.

Charles Darwin

How old is the theory of evolution?

Aristotle came up with the first theory about life on Earth and he believed that species were fixed creations arranged by their complexity, and those ideas alone lasted for 2000 years. Lamarck later discover that change occurs over a long period of time and he discovered that in the early 1800s. Finally, in 1859, Darwin published his book about his theory of evolution (On the Origin of Species by Natural Selection.) This encompassed his findings from his voyage on the HMS Beagle in 1831-36 on divergent evolution of finches on Galapagos Island and also his research in Australia.


What are the two broad processes that make evolution possible?

Answer 1

Two broad processes that make evolution possible are 1 : directional forces including mutation , migration and selection and 2: nondirectional forces that include random genetic drift , bottleneck effect , founders effect ,and chance variations .

Answer 2

Evolution is most commonly described as a combination of reproductive variation and differential reproductive success.

Reproductive variation in itself is a "non-directional" phenomenon, that produces mostly random variations. Differential reproductive success (or: natural selection) is a "directional" phenomenon, that basically acts as a mechanism limiting the set of "directions" produced by random variation.

Cell Biology (cytology)

Where do you expect genetic differences between cells to arise from mitosis or from meiosis?

Genetic differences arise during meiosis due to crossing over , independent assortment/random segregation and genetic mutations, which result in variation.


When did apes and hominids diverge?

The first fossil remains that have been found were dated around 4.4 million years ago. These were the fossils of Ardipithecus Ramidus, which lived 1 million years before the last fossils that were found.

History of Science

Is evolution reversible?

Answer 1

Evolution is not a process that can be reversed. The core principle behind evolution is that traits with a positive impact on survivability or reproduction tend to passed on to subsequent generations. Evolution itself is merely the slight alteration of a species gene pool over many generations. Perhaps you can see that the question "Is evolution reversible is something of a misnomer. Is the process by which you change something reversible In certain processes the thing that is changed can be returned to its original state, but this process also requires change. If you intended to reverse an evolutionary process the only way you could do so would be through evolution. This type of process has no non-reflexive logical inverse.

Perhaps what the question intended to ask was whether a species could "revert" back to a "less evolved" state. An example to explain this would be the reversion of humans to a more apelike genetic structure. This is certainly possible. If traits that were more apelike positively impacted the survival rate or the reproduction rate of the humans that had them than humans would begin to evolve to become more and more like our simian ancestors.

Answer 2 : There are certain examples of reversal in evolution .Most familiar trend can be seen in evolution of Dinosaurs which were of small size in Triassic period , evolved to maximum size in Jurassic period ,and again decreased in size in Cretaceous period .

Answer 3: The process of Evolution doesn't have a "direction", it doesn't favor one type of organism or trait as being "higher" than another. So in a broad sense evolution simply goes where environmental conditions dictate, there's no backward (reverse) or forward.

Could traits that were once non-adaptive reappear in a population if environmental conditions changed to make them adaptive again? Yes

Can an individual organism reacquire older traits that were not part of it's original genetic makeup? No

Do some older traits occasionally reappear in vestigial form in some individual organisms. Yes (there are instances of humans being born with a short tail etc.)

Answer 4

Evolution is basically a stochastic phenomenon. In order for evolution to "back-track", every single change in the genome that had occurred would have to be reversed in the exact reversal of the order that they occurred in. This is so extremely unlikely to ever occur that, were it observed, we would have to conclude aliens were pulling our legs.

But although evolution is not reversible, it is possible for traits to evolve a similarity with an earlier form. Consider for instance the fish-like shapes of whales: they evolved from land-dwelling mammals, which in turn can trace their ancestry back to early fish. Same shape, completely different genetics.

Answer 5

If you cloned an extinct animal, it might count as evolution going backwards. Not sure about that though, cause it's a pretty philosophical question.

The Bible

How do naturalistic evolution and special creation differ in regard to this change?

Evolution means changes over time to fit and live in the environment. Special creation means the beliefs that a divine being caused all of creation as in the Book of Genesis. It is a literal translation and not based on scientific facts.


How many years have trees existed?

About 360 million years. (After the Cambrian period 550 million years ago, or "Cambrian explosion", as it is known, when most animal life began on this planet, plant life began to appear. The first plants, in the ocean, appeared 460 million years ago, and the first trees about 100 million years after that.)

Answer 2 :

Trees must not be confused with plant ! Word trees is reserved for tree ferns , gymnosperms and angiosperms , which appeared in late Paleozoic Era nearly 400 million years ago .

Farm Animals

What is the related change in two or more species?

That is co-evolution.


When does stabilizing selection occur?

When the average, or mean of a population of organisms are selected for. The immediate environment admits of only one way a garnering resources, for instance. Thus, the extremes of the population have lesser chances of survival.


Why was the urey-miller experiment important?

Answer 1

It suggested that complex organic molecules, the constituents of life, might have been created on the early Earth from existing inorganic chemicals. This left open a possible source for abiogenesis, rather than life being brought here from elsewhere in the universe.

Answer 2

The Miller-Urey experiment demonstrated that it is possible for complex organic elements to spontaneously form under abiotic circumstances, one of the key requirements for any potential explanation for the emergence of life on Earth. It was later shown that Miller's assumptions about the atmosphere of pre-biotic Earth were off, however, similar experiments have been done for various types of atmosphere, with similar results: a broth of diverse complex organic molecules, up to and including polypeptides and amino-acids.

Charles Darwin

How does coevolution differ from evolution?

It doesn't. Co-evolution is simply a special case of evolution in which two or more species affect the direction of one another's evolution. The classic example is predator/prey interaction. All rabbits are variants and all fast rabbits vary among themselves also, with the faster ones surviving to reproduce ever faster rabbits. ( within physical limits and incrementally; think of how humans have shaved time off the mile run in the last 50 years ) This drives the evolution of faster, within limits, predators to chase these rabbits. Thus you get a arms race of coevolution in two interacting organisms.


What are an Alligator's adaptations?

An alligator's adaptations include:

  • A long and powerful tail for swimming and defense.
  • Nostrils on the top of the snout so the alligator can stay mostly submerged in water while approaching prey.
  • Rows of conical teeth that make it easier to capture and hold prey.
  • A tough waterproof hide which is also a good defense.
  • A four chambered heart that is metabolically efficient.
  • Webbed and clawed feet that help them with swimming and digging.
  • Massive jaw muscles for feeding.
  • Camouflage in swamp waters so they can catch their food

How does adaptation helps the mustang survive?

Truthfully, the American Mustang has very few natural predators. There isn't much to stop them from surviving in the wild except maybe the elements and human interference. Technically, they are an invasive species as they are not native to the Americas. The current Mustang isn't even related to the horses brought over by the Spaniards as wild Mustang populations have been culled many times over the years. There were even times when complete eradication was attempted.

However, to the point, Mustangs naturally have thicker hooves than many other breeds of horses. This has to do with the terrain they live on. It only takes a few generations of horses living on rocky ground to result in thicker than average hoof growth. They also have a thicker and hardier structure than many other breeds. What they lack in speed and agility they make up for in ruggedness and endurance. Their bone density is also very high, making them less prone to injury.


What are the character states shared by the ancestor or outgroup of a clade called?

Plesiomorphy. Shared '' primitive '' characteristics of the ancestor or outgroup of a clade.

Human Anatomy and Physiology

Can the fight or flight instinct be traced to a physical location in human biology?

The sympathetic nervous system, more specifically, fight or flight response is mediated through the hypothalamus.


What period of time did ammonites live in?

This cephlapod suborder existed from the lower Triassic to the upper Cretaceous. All of the Mesozoic Era.


Why does thermodynamics not preclude the evolution of life on earth?

A common creationist misconception is that the Second Law of Thermodynamics prohibits things getting more complex. The law is usually misrepresented as demanding that "everything runs down." But if this were true, not just evolution would be impossible, but also the growth of an adult human from a fertilized egg cell.

The simplest counter to the creationist argument that "thermodynamics precludes evolution" is to observe that the second law does *not* prohibit a temporary, localized reversal of entropy. In the case of life on Earth, the laws of gravity and chemistry, combined with the energy provided by the sun, provide the engine that drives a localized, temporary (on cosmic scales) reversal of entropy.


How do scientists use biochemistry to determine relationships?

The biochemical pathways that exist between organisms that also have close physiological homology strongly suggest common ancestry. Even organisms that look nothing like each other have very similar biochemical pathways. The amoeba and you, both being eukaryote, have mitochondria that use the biochemical pathway of oxidative phosphorilation.

Traditionally, biologists looked at visible characteristics to try to work out the relationships between organisms. This isn't always very reliable, because often two species will develop similar adaptations for the same reason. For example, dolphins/whales have most of the same adaptations as fish for living in water, even though their ancestors lost the ability to live in water. Koalas are often called koala bears, even though they're not bears. And so on. But I think that this isn't much of a problem if you look at DNA/protein. For example, the genes for fins in whales would be different from the fin genes in fish (unless those genes have been present but inactive in the land-dwelling ancestors of whales, which is possible).


What is inorganic evolution?

Inorganic evolution is the theory of the creation of the universe, not of the species of animals found on earth (ie organic evolution). It does seem to be a point of contention among a few as how this led to complex compounds. There is no connection as no scientific evidence has shown it, yet.


What is evolutionary relatedness?

a time line of shared ancestry between groups.


Why is it difficult for the systematist to classify asexually reproducing organisms as a species?

Asexually reproducing organisms do not interbreed.

In sexually reproducing organisms, speciation is defined in terms of the hybridisation rate between populations. In other words, how often males and females from separate (sub)populations mate with one another. In asexually reproducing organisms, hybridisation does not occur in this manner, so a different definition for speciation is required. In single celled organisms strains are usually considered separate species when their genomes differ from one another by a given percentage.

Zoology or Animal Biology

How did animals come to be?

Answers from various perspectivesArguments for Creation Theory
  • Creationists and Intelligent Design scientists believe animals were created as kinds, and that variations within those kinds have occurred over time by adaptation and by manipulation, such as the genetic selection of traits by breeders of pets and livestock. Evolutionary scientists usually believe complex animals evolved from simpler life forms. They do not generally explain how the simple life forms, which are also animals, came to be, although some believe that non-living protogenic amino acids may have combined and generated life forms.
  • Creation Theory is that all life comes from created kinds. There is no argument against speciation. All changes in life forms are micro-evolution, and do not add complexity or genetic material. The fossil record shows fully formed abrupt appearance and stasis (no change) in each layer. Even evolutionists admit this fact.James Crow, a modern leader for evolution theory admits, "...the details (of how evolution could have taken place) are difficult and obscure." (The Twilight of Evolution, p.48) Almost all the touted proofs for evolution show only micro-evolution (eg. Darwin's finches, the peppered moth, antibiotic resistent bacteria), which is not disputed by Creationists or Intelligent Design proponents. These changes have no increase in complexity, but merely emphasize certain pre-existing traits over others. Evolution Theory totally and directly contradicts the well-proven Second Law of Thermodynamics--the universal law of increasing entropy. Things tend toward disorder over time, unless there is outside influence. A common misconception is that 'change equals evolution.' Animals change or adapt to their environment because they already have the inbuilt genetic ability to do so. No new genetic information is added or written into the genetic code. It has also never been demonstrated that chance random processes can generate anything remotely like life. Biochemistry clearly demonstrates that even the simplest cell is incredibly complex and is easily destroyed. Water is particularly destructive. If even the simplest cell cannot arise spontaneously, neither can anything else, including the animals.
  • Animals came to be God creating them. Every building has to have a builder. If you start there that at least states there has to be a higher power! Everything in the Bible is true and not one thing has ever been proven wrong.
  • In Genesis 1: 20 God said, "Let the water teem with living creatures, and let birds fly above the earth across the expanse of the sky." In Genesis 1: 24 he said, "Let the land produce living creatures according to their kinds: livestock, creatures that move along the ground, and wild animals, each according to its kind." We know that the Bible is the true, inspired Word of God. So how much more proof do you need? Maybe in the beginning of the world, animals and humans lived longer, so you won't find many fossils of them. The world was pure before the Fall of Man, and we don't know how long the time between the Creation and the Fall of Man. It could have been centuries, or years, or days, or seconds. But maybe that is why you don't find many fossils of animals in the first layers of earth. And God didn't see fit to tell us how everything fit together. He just told us what we need to know, and we need to accept that. So, animals were made on the fifth and sixth days of creation.
Arguments against Creationist Theory
  • The fossil record shows the gradual emergence of different, and generally more complex species over time. For example, the oldest layers only contain bacteria. Newer layers contain mollusks, invertebrates, etc. The newest layers contain vertebrates.
  • Creationist Theory does not explain geographic distribution. The most closely related species are generally also found in the closest proximity to each other.
  • Creationist Theory does not explain vestigial structures. Vestigial structures are the leftovers of evolution that are no longer functional. For example, wings on flightless birds, remnant hindlimb/pelvic bones in whales, tailbone on humans. If we were created, why the extra spare parts?
  • Creationist Theory does not explain why species' designs contain flaws. With evolution, flaws can be passed down from ancestors. Evolution only selects for the best available, but does not guarantee that the best is without flaws. Sometimes it requires a trade off. For example, primates (including humans) have a non-functional gene for synthesizing vitamin c because presumably ancestral primates had so much vitamin c in their diets from fruit that the gene was not necessary. The gene is still there, but unlike in other animals, it doesn't work, so now that our diets don't always contain enough vitamin c, we can get scurvy. Another flaw in our design is that our windpipe stems from the throat so it can be easy to die from choking. If we were simply created, then why would there be these flaws in our physical design?
  • Where is the mixing of features? If animals were just created, wouldn't there be a more random mixing of features? Instead, you have groupings of species sharing many similar traits as if they were related to one another or evolved from common ancestors. For example, mammals are grouped because they all produce milk. But all mammals also are warm blooded and have hair or fur (even whales have vestigial hair in the fetal stages). Where are the feathered mammals? Where are the birds that bear live young? You can find the features of older groups appearing on groups that evolved from these groups, but you don't see traits from more recent groups on species from older groups. Sure, there are a few anomalies out there, but do a little research and evolution explains why.
  • Creation is just one possible explanation for the origin of life on earth. There is no single way to demonstrate how life began. Any who claim creation are not necessarily correct. It's a war of words. Of philosophies and ideologies. And it is likely to remain so for some time. Until then, just about any argument concerning the origin of life on earth is as "valid" as the next. The Bible thumper is no more or less correct than the one who thumps a science text. Believe what you want to. But your beliefs do not invalidate those of others.
Arguments for Evolution Theory
  • All the proof one needs to see the changes evolution has effected are at hand. The earth has changed dramatically over the billions of years since it was formed. When life began (by what mechanism one is free to speculate on), it began a long, long time ago. As the planet changed, the life changed, evolved, to adapt to the new conditions. Or it died. It's that simple. The ideation of the tree of life (by Linnaeus) was a brilliant stroke. Modern evolutionary synthesis (MES), the state of the art construct that deals with evolution, is fact. (We just disagree amongst ourselves about abiogenesis - the mechanism of life's inception.) Many Christians are on board with MES and modern science's take on the age of the earth. Literal interpretation of the Bible leads to severe ideological conflicts. But some believe in a young earth. This seems to be adherence to obviously flawed ideology. Particularly in the face of the mountain of facts that any individual could understand. To evolutionists, young earth Christians seem to practice a form of denial on an epic scale. Intelligent Design Science is pseudo-science. It is an ideology that appears to have been designed for a single purpose: to get creation taught in public schools. The basic laws of existence state that nothing comes from nothing. However that would not preclude the possibility that life can come from nonliving things. Protenogenic amino acids are not alive, and neither are the proteins they create. However, a simple combination of proteins with the necessary levels of carbon, hydrogen and oxygen to form strong bonds could very well result in single celled organisms, which, through symbiosis could bond with others and create multi-celled organisms. These things can occur spontaneously. Science has not demonstrated they did occur that way, but it would be foolish to deny that it is possible. There is no way to prove that life here on earth did not come from somewhere else. It could have, and there is more than one explanation as to how it could have occurred.
  • Some molecules, acids, a pool of lava and luck.
Arguments for a Combination of Creation and Evolution
  • If something needed to put the 'objects in question' into motion in order for them to even have a chance to bond into life, why can that not be the case to evolutionists? There is still room for evolution after the cause of motion. Also, why can the world and all life within it not have been intelligently designed but designed to evolve?
Arguments via straight up Factual Science:Below are scientific facts that clarify the most common misconceptions about 'How animals came to be':

Claim: All changes in life forms are micro-evolution, and do not add complexity or genetic material.

The Science- This is simply not true. New genetic material passed through the filter of natural selection easily gives rise to complexity. Such complexity can be seen in the case of a nylon-eating bacteria. New genetic material can come about by various mechanisms. The two most dominant ones in vertebrate evolution are genetic recombination and genetic mutations. These are widely studied phenomena and have an extremely well documented scientific basis.

ClaimThe fossil record shows fully formed abrupt appearance and stasis (no change) in each layer.

The Science- I can only imagine that the author is referring to the Cambrian explosion, which is a well documented event in geology. Furthermore, there have been found countless precambrian fossiles, and first solid evidence of life dates back to roughly 3.5 Bya.

Claim-Even evolutionists admit this fact.James Crow, a modern leader for evolution theory admits, "...the details (of how evolution could have taken place) are difficult and obscure." (The Twilight of Evolution, p.48)

The Science- This is a case of quote mining and, even if quoted correctly, isn't evidence for anything. What one scientist, or any person, says about his own personal incredulity says nothing of the viability of a theory.

Claim-Almost all the touted proofs for evolution show only micro-evolution (eg. Darwin's finches, the peppered moth, antibiotic resistent bacteria), which is not disputed by Creationists or Intelligent Design proponents. These changes have no increase in complexity, but merely emphasize certain pre-existing traits over others.

The Science- I cannot emphasise the error of this statement. I return to the case of the nylon-eating bacteria, where nylon is a polymer first synthesised in the lab in 1935 by Wallace Carothers. "Macro-evolution" (mind you, biologists and geneticists alike do not differentiate between the two) is merely the result of accumulated "micro-evolution". Whereas 1+1+1=3, 1+1+1+1... would eventually equal 100, enough for one to call it macro-evolution by the "micro-macro" standard.

Claim-Evolution Theory totally and directly contradicts the well-proven Second Law of Thermodynamics--the universal law of increasing entropy.

The Science The Second Law of Thermodynamics explains how entropy tends to increase in a closed system. The way this law interacts with biology is that organisms must fight the tendency for disorder lest their cells will collapse. This is the purpose of homeostasis, a process which every organism shares. It has absolutely nothing to do with the increasing complexity of the global gene pool. Apples and oranges!

Claim-Animals change or adapt to their environment because they already have the inbuilt genetic ability to do so. No new genetic information is added or written into the genetic code.

The Science - This is a statement which simply contradicts modern research. I have already written a great deal about mutations and its mechanisms, so I won't comment further.

Claim-It has also never been demonstrated that chance random processes can generate anything remotely like life. Biochemistry clearly demonstrates that even the simplest cell is incredibly complex and is easily destroyed. Water is particularly destructive. If even the simplest cell cannot arise spontaneously, neither can anything else, including the animals.

The Science- It has been demonstrated that amino acids can be synthesised using only a mild electric current from where there were once only simple gases such as, among others, H2O (water vapour), CO (carbonmonoxide) and CH4 (methane). Furthermore, this has nothing to do with evolutionary theory. This is an entirely different field of study altogether called Abiogenesis and is in the field of Organic Chemistry rather than Evolutionary Biology. More importantly, Evolutionary theory is not dependent on Abiogenesis, and Abiogenesis is not dependent on Evolutionary theory for either to be true. This statement supposes that this is the case.


What are the 5 relationship in your ecosystem?

1. Mutual-ism

2. Predation

3. Parasitism

4. Commensalism

5. Competition


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