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.

  2. Mutations.

  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 have 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, why has no one species over the course of hundreds of millions of years been fit enough, or advanced mentally as we have, or even in any slightest bit?

  • $\begingroup$ 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? $\endgroup$
    – jamesqf
    Commented Jan 3, 2015 at 22:56
  • 3
    $\begingroup$ Cockroaches have changed quite a lot, modern cockroaches are very different from cretaceous cockroaches, there is also quite a variety of them (and that's without including termites). saying they are the same is like saying humans and lemurs are identical becasue we are both primates. Your premise is based on your own lack of knowledge about the organisms not a real lack of change. $\endgroup$
    – John
    Commented Mar 24, 2017 at 15:23
  • $\begingroup$ People with extensive knowledge in evolutionary biology won't say list these three elements as the three ways evolution happen! $\endgroup$
    – Remi.b
    Commented Nov 10, 2017 at 19:43
  • $\begingroup$ Would you notice cockroach evolution if it happened? In fact, there is a recent example of evolution in common household cockroaches: they've evolved to resist the sugary baits used in traps: livescience.com/34647-cockroaches-evolved-avoid-baits.html $\endgroup$
    – jamesqf
    Commented Nov 10, 2017 at 19:53
  • 1
    $\begingroup$ Just in the last 100 years we've seen peppered moths change color, drug-resistant bacteria, pesticide-resistant bugs, metal-tolerant centipedes, and so much more. Other animals are evolving quite well in fairly obvious ways. $\endgroup$ Commented Jan 3, 2018 at 0:00

5 Answers 5


How come most animals never seem to evolve over millennia?

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 of thousands of years. But what do you know about that (no offence here)? Have you actually reviewed many kinds of 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 a better sense of smell. This is a biased 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 the 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 the 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 the 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 depend 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 are a lineage with high evolutionary rate.


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?


This is a tricky question. First, evolution tend to be slow, although there have been recent examples of very fast evolution as well. So for most evolutionary processes, we are not present long enough 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 as 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 endemic species developed (see here) which was then reduced by pollution and other environmental problem. The remaining species are evolving again to occupy 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 species (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 anymore. And with 7 billion of us now present, it's not that easy for mutations to come through at our reproduction rate.


In response to this part:

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?

All animals are the result of evolution, which includes mutations.

Now, what you should understand is that evolutionary changes have to be selected for, but also must be immediately useful to the organism if they cost more.

There is a long term tendency in our lineage towards increased brain sizes. Animals -> Mammals -> Primates -> Humans. This long term development need not have happened in the first place. In the Jurassic Period, the most successful group of animals were dinosaurs, who in general had small brains.

In addition, our brains require far more calories than the brain of, say, a chimpanzee. Even if you have a lineage that, over the generations, has a tendency towards larger brain sizes, it would also need to be able to hunt or forage more in compensation for the increased caloric needs. If it were not able to do so, a larger brain would actually be a profoundly negative characteristic, a useless drain of energy.

In addition, the benefits of increased intelligence are highly circumstantial. Consider if you gave a cheetah all the brain power of a human. It might then understand that if it dug a hole and placed fake grass over it, it could catch an antelope for less effort than having to stalk and chase it. Less effort means less calories expended and ultimately most of an organism's fitness has to do with how much energy it expends in trying to procure energy (calories).

But lacking opposable thumbs and hands with digits, it would be unlikely to accomplish such a thing. Also, such tasks are more efficient when done by a group, but many animals do not coordinate group-wise as extensively as humans do. So what we have is at least 3 but probably many more things which all have to come together in the same species for them to rise to the top of the food chain like we did:

  • Dextrous limbs (i.e. opposable thumbs and seperated digits)
  • Brains tripled in size (relative to other species of ape)
  • Behavior of extensive group coordination (tribes)

As you can imagine, a species evolving our intelligence and using it to dominate the local ecosystem as extensively as we do is therefore a rarity.

  • $\begingroup$ You have put high effort for an answer, but please consider adding some references to your answer. $\endgroup$ Commented Mar 24, 2017 at 14:10

Evolution is an ongoing process; it has no predetermined goal or direction; it never stops. Nothing ever stops because everything is ever-moving, ever-changing.

Is man more intelligent now than few thousand years ago? Has mankind a better understanding of the phenomenal and noumenal realms now than the people who composed the Upanishads, the Brahmanas, the Vedas ~2,500 years ago, which was preceded by hundreds if not thousands years of oral transmission (myths) from generation to generation?


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