Why only Homo sapiens...?

Question

Of all the species that have ever existed, why is it that only man has evolved an incredible brain that separates him from all other species? It seems to me that the theory of evolution suggests that there would be various levels of intelligence, making a gradation from beasts to homo sapiens. Why is there such a huge, huge gap between mankind and the beasts? I am looking for a rational, scientific opinion, not spiritual.

I do not deny that other creatures have some level of intelligence, and when they perform actions that look like human actions, we tend to ascribe higher levels of intelligence to them. The levels of intelligence between these animals can be charted highest to lowest. When man is added, it goes off the chart and into the stratosphere by comparison. Why?

Answer 1

> It seems to me that the theory of evolution suggests that there would be various levels of intelligence, making a gradation from beasts to homo sapiens. <

First, the theory of evolution suggests no such thing. While a trait A invariably *evolves* in gradations, there is no reason all that intermediate forms have to continue to exist ... or that the exact same trait would evolve many times independently in other creatures.

A girafffe has a very long neck. No other species comes close to the proportions of the giraffe neck. And yet there is only one species of giraffe (albeit with many subspecies). Why? Because most (if not all) the evolutionary history of the giraffe has been in a well-defined area of Central Africa ... so there has been little pressure (or not enough time) to form genetically separate populations where one population can evolve into a completely separate species. So the species as a whole underwent *huge* growth in height in a relatively "short" amount of time (in geological terms). And no other species on the planet happened to develop that particular trait (an enormously extended neck).

The same with the elephant's trunk ... only three living species. And no other animal has even close to such a developed trunk. And there are *many* other examples of traits that got almost freakishly overdeveloped in a single line (order, family, genus, or species), and in no other. It's actually a much more common occurrence than you might think.

Second, intelligence is no different from any other trait like a long neck or trunk ... at least it is no different as far as evolution is concerned. Old World apes, as a group, developed unusually large brain capacity relative to the other primates. Among these, it appears that one group branched off about 6 million years ago and began a period of *unusually* fast brain growth ... equivalent to the growth of the giraffe's neck or the elephant's trunk. Why? There are a few theories ... e.g. that the development of an articulate voice box, and the invention of language, itself spurred a corresponding massive expansion in the certain regions of the brain.

But the point is that the reason *why* this occurred doesn't matter (for this question). Only the fact that his was very rapid in geological terms (which is confirmed by fossil evidence), and that this expansion occurred in an isolated region, the part of central Africa where all Homo species originated. And second, that this expansion did not occur to such a freakish extent in any other line on the planet.

The result is that only three species of Homo (that we know of) proliferated and spread to other parts of the world. Two of these species (H. neanderthalensis and H. floresiensis) eventually died out ... as recently as only 20,000 years ago. (In fact, there is some speculative evidence that H. sapiens, may have been responsible for wiping out the last of the neanderthals.) This left H. sapiens the sole beneficiary of the specific type of brain expansion that occurred in our particular genus (Homo).

There is nothing *illogical* about any of that. And the fossil and genetic and molecular evidence are all independently consistent with that theory ... as they are for the theory of the development of the giraffe's neck and the elephant's trunk.

Third, and finally, human intelligence is not the only form of intelligence that has appeared on the planet. It has certain characteristics that make human thought very different ... e.g. with complex language and technology. But cetaceans (whales and dolphins) are generally considered to have evolved a completely different type of intelligence that is difficult for human intelligences to fully comprehend. And other examples have arisen in other mammals, a few birds, and even an occasional invertebrate (like cephalopods). But all of this just shows that a large brain is just another trait, no different than large eyes, or articulated limbs, or complex vocal cords.

Answer 2

Think about how mankind has behaved during it's recorded history. We have continuously explored and moved into new areas to exploit the resources. When we have come across other members of our species living there, what have we done? We have fought for control of the area and the resources.

When we fight, we keep going at it until one side wins. In recorded history, it is probably reasonable to say that both sides would be of equal intelligence. The winner has been determined by technological developments. As an example, and iron sword betters a bronze sword, gunpowder betters arrows and so on.
In some cases this has resulted in whole tribes or nations being wiped out.

Now imagine a situation in very early history where there may have been two or more similar creatures with different levels of intelligence. The more intelligent would most likely develop new weapons or tactics quicker than the less intelligent. Guess who wins? This would certainly create an intelligence gap between the most intelligent and the next most intelligent.

The process is, of course, not just limited to fighting and weapons. Other technology such as farming, building and so on would make it easier for the more intelligent to support larger communities and to survive in harsher conditions. Transport developments allows the control of larger areas and the ability to use resources from larger areas.

Answer 3

First of all there is a gradation of intelligence amongst different animal classes and within mammalia.

For example grey parrots are very intelligent at problem solving and logic and are the smartest of the bird species, octopuses have been observed "playing" and may have the intelligence of a cat or dog, that's pretty clever for a mollusk.

Our relatives in the animal kingdom, chimps, bonobos and gorillas are not dumb, dolphins are probably second only to humans in intelligence. We just happen to be on the top of the IQ pyramid.

But there are lots of other attributes we are way down the scale on. IQ was probably our survival tool.

Second: Nature has show us time and again that its not the "smartest" but the most adapted to their environment who survive. Take a smart human, with no technology, and a dumb salt water fish, throw them in the middle of the ocean and see who survives longest.

Third: There are lots of "huge gaps" in physical abilities of species (frogs are some of the best leapers, sea snakes have ultra deadly venom, hummingbirds have the fastest wing cycles etc...) so why should intelligence be different?

Fourth: There were very intelligent hominids evolving alongside homo sapien. They were wiped out (maybe by us, disease, climate) and we just came out on top.

Answer 4

The neanderthals were a species that branched off from the line that led to us. They were quite intelligent and if they had not died out, we'd be living with their descendants today.

But don't forget about animals like dolphins that show a very high level of intelligence. They have their own language, individual names for each other, a sense of self-awareness, excellent reasoning ability and have even been shown to gossip like humans. It makes you wonder what they'd be capable of if they lived on land and had a humanoid form.

Answer 5

There IS no 'rational, scientific' reason for it. Either it 'just happened', the way war and crime and hate and prejudice 'just happen', or it was caused by a person, the way war and crime and hate and prejudice are caused by persons.

My point is that if we as persons were not made by a person but by blind impersonal forces, then we are not really persons and not responsible for what we do, no matter how it seems to us.

This is an excellent question, but it really belongs in the humanities/ philosophy section, because it touches so strongly upon the question of whether right and wrong really exist, or if 'might makes right.'

Answer 6

Darned good question! And one that science has been struggling with for a long time. Of course Arthur C. Clarke offered one idea in "2001: A Space Odyssey"