Evolution? How?

unless, like in the differences in humans, chimps , and other great apes where a specific set of chromosomes (like no. 2 in the case of humans) become fused.
Although thats quite a stretch for dogs and cats.

Now that Rex has brought this up, I could kick meself (and you too p'dog) for "The wonder squirrels" argument about no new genes ever. When we have entire chromosomes that have rearranged or fused.
Duhh, and the DNA evidence favors the similarity of fused patterns in the karyotypes ( i think thats the correct term).
I heard today that the genome projects are looking at sequencing Hiraxes in the next batch of animals. Also Sireneans and whales. I think the evolutionary implications are immense. Of course, I wouldnt expect the Dembskis and Behes of the world to give in to any darn "evidence"

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Look at the bones guy getting all excited about molecules...

Wunderskurrel's arguments are independent of any observation. In his eyes, genes are complex, and could not possible arise de novo. Noting any instances where this appears to have heppened simply strengthens his/her argument, as far as (s)he's concerned: just a recitation of impossible events.

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You guys are awesome! Thanks for answering my reply. I really admire you all for your knowledge and insight.

I didn't know that dogs and cats were so different genetically... That really surprised me.

I think mutations are the way to go but convergence is an interesting possibility.

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It's conceivable you could get morphological convergence with highly selective breeding over a number of generations, especially since you're talking about closely related critters (carnivora), but hybridization seems impossible.

(Foxes, though, also have 19 pairs of chromosomes. Makes me very curious about the phylogeny there, and whether the taxonomists might not have mis-assigned them to canidae. Perhaps that's something to look up some rainy day.)

Additional hurdle: cats, as obligate carnivores (dogs are really omnivores), have lost the ability to synthesize to synthesize taurine and arachidonic acid -- these are essential in feline (but not canine) diets. The chance that they could recover the ability to synthesize even one of these and become physiologically dog-like is extremely remote.

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I find it rather odd that scientists cannot give us a definitive answer if humans converged with neanderthal... A few years back the answer was definitely not! Now they say this is why people have big noses... They say we also converged with the very tall Africans. This is why we still have some very tall people in our race.

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Where are you getting this stuff?

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I heard it on a cable science program.

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Okay, here's some stuff about recent human history. F'man can correct me if my geological understanding is shoddy, I expect.

We are currently in the middle of a sequence of events that is perhaps unique in the history of the earth -- an ice epoch dominated by glaciation with occasional regular warming, due to inability of ocean currents to move across either pole.

The climatic fluxuations have resulted in significant waxing and waning of the population. During the bad times, the human population plummets, likely isolating different human populations. When populations are isolated, genetic drift and (perhaps) selective pressures create diversity between (but not among) populations.

During the good times, these populations expand, overlap, and gene flow perhaps results in increase in diversity within the human genome.

I'm not up on the Neanderthal question, but "big noses" seems to me unlikely evidence of miscegenation.

Anywho, that's what I've been reading, especially in "The First Chimpanzee" by Gribbin and Cherfas...

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pd, The mystery that has not been answered by science is why humans have so many "races" with different color of skin and eyes if we all originated from Africa?

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Why shouldn't it? Look at how various these attributes are among domestic dogs, all of which supposedly originate, at least in part, from two Asian wolf packs?

And there is tremendous diversity of these traits among aboriginal Australians -- and tremendous diversity among other traits (size, for instance) among the folks who stayed in Africa.

It's easy to go from dark brown to light brown to pink, anyway. It just requires a loss-of-function mutation or two -- and sexual selection might easily spread these null alleles around, especially in a small populations (which founder populations in Asia and Europe and elsewhere might very well have been.

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cicerone imposter wrote:

pd, The mystery that has not been answered by science is why humans have so many "races" with different color of skin and eyes if we all originated from Africa?

That's a strange thing to say, when in my A-Level Biology course, the first thing we were taught about human evolution is evolution of skin colour from hotter climates to colder climates.

It's all to do with mutations, right?

Well, let's put it this way. Melanin is the source of skin colour. More melanin equals darker skin. Darker skin = more protection against UV rays, of which there are more closer to the equator. Let's face it, it's not very sunny up north, especially so in the UK.

However, more UV exposure allows for more Vitamin D synthesis in the skin. Those with lighter skin will synthesis more vitamin D.

I'm not a nutrionalist, so I'm not sure why Vitamin D is so important that the trait was selected for, but that is the general consensus on why we have different skin colours.

As for iris colours? I didn't learn about that one, but I think it might be something similar. Something to do with less intense light the more north you go?

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Wolf_ODonnell wrote:

cicerone imposter wrote:
pd, The mystery that has not been answered by science is why humans have so many "races" with different color of skin and eyes if we all originated from Africa?

That's a strange thing to say, when in my A-Level Biology course, the first thing we were taught about human evolution is evolution of skin colour from hotter climates to colder climates.

It's all to do with mutations, right?

Well, let's put it this way. Melanin is the source of skin colour. More melanin equals darker skin. Darker skin = more protection against UV rays, of which there are more closer to the equator. Let's face it, it's not very sunny up north, especially so in the UK.

However, more UV exposure allows for more Vitamin D synthesis in the skin. Those with lighter skin will synthesis more vitamin D.

I'm not a nutrionalist, so I'm not sure why Vitamin D is so important that the trait was selected for, but that is the general consensus on why we have different skin colours.

As for iris colours? I didn't learn about that one, but I think it might be something similar. Something to do with less intense light the more north you go?

I have heard too it takes 10,000 years for the sun to change the color of skin. If it was genetic we would not see such a gradient in peoples. We would see white skin appearing in the middle of black cultures and vice versa. I believe scientists are in agreement that skin color is not genetic but environmentally produced. As for eye color we know that is genetic. Dominant and recessive genes dictate eye color. Black people can have blue eyes. Although I have not heard anything about blue eyes being more susceptible to sunnier climates that sounds highly plausible.

This all comes back to the idea that the sun creates plasma and can possibly effect our genes...

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Something about skin color and the movement of techtonic plate during the past millions of years just doesn't seem to jive in my head. Maybe somebody can explain it to reconcile these variables.

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Why don't we see more differences between humans from such far away places? More than just skin color, or fatty concentration.

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cicerone imposter wrote:

Something about skin color and the movement of techtonic plate during the past millions of years just doesn't seem to jive in my head. Maybe somebody can explain it to reconcile these variables.

c.i. This may help you out a little.
The Journey of Man

Be sure to check the photo gallery. There used to be a very good interactive page about the migration, but it does not seem to be available any more. If I am reading the schedule right, the program will be replayed on June 18, and 19.
Schedule

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mesquite, The link you provided is probably the best I've seen on this subject, but it still leaves many questions unanswered; too many caveats. With the advance in technology and unearthing of older fossils, maybe we'll have a better grasp of what happend in the development of homo sapiens.

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c.i. There is a whole lot more info on this link.
Genographic Project.
You can even contribute your own DNA.

The interactive Atlas has a lot more info than is obvious at first. You can explore different time periods. Clicking on the genetic marker migratory routes opens new windows with info and photos of the representative populations carrying the markers.

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thunder_runner32 wrote:

Why don't we see more differences between humans from such far away places? More than just skin color, or fatty concentration.

There are some other differences, but evolution is slow compared to the lengths of time these groups have been separated.

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Brandon, The length of human evolution is a confusing one, because some scientists claim it's short and some claim it's long. Added to this confusion is the fact that this planet experienced an ice age during this period of evolution. Somebody needs to get this all organized in a way with some consistency so it makes sense.

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cicerone imposter wrote:

Brandon, The length of human evolution is a confusing one, because some scientists claim it's short and some claim it's long. Added to this confusion is the fact that this planet experienced an ice age during this period of evolution. Somebody needs to get this all organized in a way with some consistency so it makes sense.

Uh Huh!

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