Evolution - Have you ever thought about...?

Qcmbr

Why out of all the species that exist only humans seem to be radically different in every shape and way?

Its almost as if humans have stopped 'evolving' and have started to diversify in looks rather than in additional mutations.

All haddock look pretty much the same as each other, daisies are pretty much just daisies etc.. in fact it seems that the greatest variety within a species seems to be when artificial means are used (domestic cats, dogs etc..)

Do our evolutionary friends have any explanations as to why humans look totally different (even within families) whereas most animal species look incredibally uniform within their species?

I don't think that there are many evolutionary pressures at all on humans because we have the ability to mould our environment whereas animals seem very limited in altering theirs.

hamsterbait

The huge differences in looks one sees among humans of european descent is due to the fact that europe is a huge genetic melting pot caused by changes in climate over the last 15, 000 years.

Go to other parts of the world where there was very much less mixing of genes and most europeans would say they all look so alike!

Japanese, chinese, vietnamese, korean, african tribes, South american tribes. To most western eyes these humans all look the same. Because europeans are such a mongrel breed, we don't even need to look closely at each other to be recognised. If there had been a Noah's flood in the last 6, 000 years there would be nothing like the diversity based on environmental conditions that we find.

Mitochondrial DNA in Africa is the most diversified, yet because of geography, inbreeding means that each part of africa has its own very distinctive human physiognomy. Possibility of interbreeding for these people has occurred so recently, that we do not find the wide variety of external differences found in europe.

HB (of the all hamsters look the same class)

AlmostAtheist

Funny you should ask, I was just thinking about this the other day. Michael Crichton has a book called Travels where he describes the places he's been and experiences he's had. It's a good book, though it makes me long to be rich enough to do all that stuff!

In it, he described visiting a family of gorillas. The leader of his group pointed out the various members of the group and mentioned their characteristics and temperments. Crichton admitted that he couldn't tell them apart. To him, they all looked like gorillas. But to the guide, it was clear as day which was which.

People even have trouble seeing differences in other races, hence you hear, "All white people look alike to me."

I would guess if you were a haddock, all people would look the same. I doubt there is actually such a great difference in our variation and that of the other animals.

Funnier still, I was just thinking about evolutionary pressures on humans just today. There are viruses that some people seem practically immune to, while others succumb to it. If such a virus were deadly and became common, humans would likely take an evolutionary turn toward an immunity to it. (All the non-immunes would die off, all the immunes would bear immune children.) But pressure to move back into the trees, for instance, doesn't seem to be weighing heavily on anyone. (Unless you count moving into the woods! I know plenty of folks feeling THAT pressure!)

Dave

Elsewhere

Do our evolutionary friends have any explanations as to why humans look totally different (even within families) whereas most animal species look incredibally uniform within their species?

I suspect this is an illusion. Humans are most familiar with humans so we are able to notice the subtle differences in each other more than we do in other animals.

As an example we can look at names. In a given region you can tell which area people are from... Smith is "American" and "Duncan" is Scottish. If you go to a region you are not familiar with, such as the Middle East, I seriously doubt you would be able to discern the differences between the different ethnic Arab names while the people who were raised there can tell the difference. Adnan al-Dulaimi is a Sunni name and Ahmed Chalabi is a Shia name. As westerners we cannot see the difference but an Iraqi can tell without even having to think about it.

Daunt

One idea that seems pretty cool from an evolutionary standpoint is that our desire to see beauty in the most subtle and intricate of ways may have contributed to the differences of people. I can't identify all of the aspects of love and attraction because frankly I don't know, but it's something cool to think about. Infact I'ma have to look in it, sounds terribly interesting already.

kid-A

Its really just a question of geographic distribution and the associated levels of sunlight, elevation, dietary differences. Gorillas, Chimpanzees, Orangutuangs and rhesus monkeys all share a common ancestor but they look radically different from each other simply due the environments they evolved in. WHats interesting about humans is that 'race' is largely a biological illusion, the differences are cosmetic, genetically we are more similar then different.

Daunt

The differences are miniscule. On a scientific level, there's barely anything seperating them.

sonnyboy

Do our evolutionary friends have any explanations as to why humans look totally different (even within families) whereas most animal species look incredibally uniform within their species?

As a rule, lions don't mate with tigers (even though they can). There are no 'pure' breeds of humans because we take it upon ourselves to breed with whichever race we see fit. Edit: We're much like dogs in that aspect. You rarely see two mutts that look alike.

DanTheMan

I can't recall all the details, but I was watching something on TV one time where these scientists were breeding wolves, a species that in its wild state tends to follow a fairly rigid form. From each generation born, they would pick the most mild-tempered and sociable wolves to mate and produce the next generation. After several generations, the wolves starting showing remarkable variations in size, shape, color, markings, etc.

So the theory was that the more sociable and docile a species becomes, the more the recessive natural variations that were in the genes all along come out to play. I think they linked the whole thing to testosterone being the genetic gate-keeper.

peacefulpete

The point has been made but just for clarity I'll mention that gentically all humans are more similar than snails of the same species on two hills 100 feet apart. Modern humans evolved as unique species very recently (a few hundred thousand years ago) and the variation that is observed is the result of adaptation and short term gene pooling. IF humans now insisted upon ridgid separation of these variations we would see some new species of homo in a few hundred thousand years but, because we have largely overcome these animal impulses, humans breed freely with variations that might have been barriors to less aware creatures.

BTW all haddock do not look the same. There are a number of variations of haddock. However, just as expected a species that moves freely in an ocean range will breed freely. This lessens the potential for variations becoming isolated populations. This in turn produces homogeny. Lake fish (perch for example) display greater variation in color and size (comparing specimens from two lakes) than ocean fish over the same amount of time for this reason.

Human variation was the result of continental isolation of populations. Snails, because of limited locomotion, tend to isolate variations, promoting faster speciation. This is why there are thousands of snail species.

Evolution - Have you ever thought about...?

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