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People often say, including those with extensive knowledge in biology, that a certain species of animal will evolve in one way or another:

1.From changing environments.


3.Possibly even genetic engineering from human animals.

My question lies in the fact that, aside from the latter option, why haven't any differences in animals'(except humans) markup, morphology, intelligence, DNA, behavior, or any habits changed over thousands or (possibly millions) of years?

A cockroach has had the same behavior it has today more than 10 million years ago, and there's been no advancements in the species in the slightest bit.

It makes you question evolution, because why don't other animals (like cockroaches) have any changes over 10+ million years, yet humans, like me and you somewhat, have, in a relative period of time similar to the linked geological period above, evolved from spear tossing hominids into someone brilliant enough to even ponder this question.

If modern humans are the result of mutations in genes, how come no one species over the course of hundreds of millions of years has been fit enough, or advanced mentally like we have, or even in any slightest bit?

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The cockroach hasn't changed because it is perfect as it is :-) Evolution isn't directed towards advancement (even when said "advancement" isn't a figment of anthropocentrism), it's driven by survival & reproduction. Cockroaches survive & reproduce quite well as they are. Absent some major change in the environment, where's the driver for change? –  jamesqf Jan 3 at 22:56

4 Answers 4

"How come most animals never seem to evolve over millenia?"

The word "seem" in your question should not be disregarded. You seem to assume that cockroaches (or most animals as you say) did not change much the last tens or hundreds thousands of years. But what do you know about that? Have you actually reviewed many research that estimate the rate of evolution of different randomly chosen lineages in the past 500,000 years? I think you assume that other species evolved slower than humans rather than know it. And you will certainly put much more importance to the evolution of the gene FoxP2 (involved in language) than to a gene allowing cockroaches to have better sense of smell. This is a bias view of what is a rate of evolution. It would be much wiser to consider a rate of evolution as something like the number of newly arising mutations that succeeded to get fixed in the population. See Haldane's rate of evolution and the Darwin unit. Please don't make the mistake to think that being smart (or complex) is some kind of goal of evolution and those that are not smart (or complex) are "less evolved" or that they evolved more slowly.

You also seem to want to point on evolution of DNA and evolution of habits. I guess you might be appreciative of the evolution of human knowledge and culture. But this is obviously something that does not have to do with genetic evolution but is rather a matter of cognitive capacity. You cannot compare change of culture and traditions of insects and humans as insects have mostly no traditions.

Now, this is obviously true that different lineages evolve at different rates. Many things influence this rates such as the population size, the mutation rate, the generation time, the selection pressure (which itself might depends on social structure or the rate of environmental change for example). In these terms I would rather believe of Homo sapiens as a lineage that should have a rather slow evolutionary rate.

Homo sapiens is quite a recent species. And speciation is often linked with phenotypic divergence, with niche competition and niche complementarity and therefore with a high rate of evolution. In these terms I would believe that humans is a lineage with high evolutionary rate.

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This is a tricky question. First, evolutions tends to be slow, alsthough there have been recent examples of very fast evolution as well. So for most evolutionary processes we are not long enough present to see them either happening or see the outcome. Therefore its also hard to say that no evolution is happening - see your cockroach example. How do you know that these animals are the same like 10 Mio years ago? And even if it is like this, it can also mean that these animals fit their niche so good, that there is not much pressure for further adaption. This can change pretty fast as examples from mites (here a report in the BBC, this is the original publication). Another example of fast evolution (of bigger animals) are the Cichlids in the Lake Victoria, which developed new after the last time the lake dried up completely something like 12.000 years ago. After that an estimated 300 endimic species developed (see here) which was then reduced by polution and other environmental problem. The remaining species are evolving again to ocupy the free niches (see here).

In the case of the human, we are pretty lucky, that no other intelligent animal has come up so far. They would have fought for the same biological niche and living space with one species eventually dying out. This has for example happened to all the other homo spcies (habilis, erectus, neanderthalensis). As a species we are quite young (around 200.000 years), so there is something going on. And there is genetic diversion between humans, but still not as much, that we cannot cross each other any more. And with 7 billion of us now present, its not that easy for mutations to come through at our reproduction rate.

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aside from the latter option, why haven't any differences in animals'(except humans) markup, morphology, intelligence, DNA, behavior, or any habits changed over thousands or (possibly millions) of years?

What evidence is leading you to that conclusion? For horses, example. (From the talkorigins article):

The first equid was Hyracotherium, a small forest animal of the early Eocene. This little animal (10-20" at the shoulder) looked nothing at all like a horse. It had a "doggish" look with an arched back, short neck, short snout, short legs, and long tail. It browsed on fruit and fairly soft foliage, and probably scampered from thicket to thicket like a modern muntjac deer, only stupider, slower, and not as agile. This famous little equid was once known by the lovely name "Eohippus", meaning "dawn horse". Some Hyracotherium traits to notice:Legs were flexible and rotatable with all major bones present and unfused. 4 toes on each front foot, 3 on hind feet. Vestiges of 1st (& 2nd, behind) toes still present. Hyracotherium walked on pads; its feet were like a dog's padded feet, except with small "hoofies" on each toe instead of claws. Small brain with especially small frontal lobes. Low-crowned teeth with 3 incisors, 1 canine, 4 distinct premolars and 3 "grinding" molars in each side of each jaw (this is the "primitive mammalian formula" of teeth). The cusps of the molars were slightly connected in low crests. Typical teeth of an omnivorous browser.

So from that, you conclude that the DNA, morphology, and intelligence of horses hasn't changed at all in 50 million years?

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Human evolution it self is major point of debate.For example I would like to give example of Dog prior to industrial revolution there were hardly 150 or bit more varieties of Dog,but after industrial revolution the no of varieties of Dog increased considerably.So till industrial revolution there were only stock varieties or which otherwise called as the wild type.So how did this change happen.It was done by controlled breeding more specifically that was called as eugenics.So same way human evolved so much as there were inter and in breeding.Which diversified our gene pool one in other way,and human from very early in the history have constantly moving exposing them to various condition which helped and still helping us to evolve and adapt.

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-1: you make a strange claim about canines with no supporting evidence or references and your point about humans is very unclear. Why would humans be inter or in breeding more than other species and what mkaes you think that is relevant in any case? –  terdon Dec 15 '13 at 15:20
well I just gave the reference to make it understand how evolution is going and why is it not happening for other organisms,and this is true for every organisms unless there is a need no one would change or going to shuffle their genome –  krushna Dec 15 '13 at 17:14
-1: I don't think this answers the question and is poorly referenced –  GriffinEvo Dec 16 '13 at 6:45

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