More than one human kind?

Question

Researchers at the University of Rochester believe they have just confirmed a controversial theory of evolution. The X chromosome is a strikingly powerful force in the origin of new species. When one species splits into two, interbreeding between the two daughter species is much more likely to produce infertile hybrids when the species exchange X chromosomes than when they exchange any other chromosomes, says Presgraves. The process, dubbed the "large X-effect," acts as a wedge between the two newly formed species, pushing them onto divergent evolutionary paths.

I once saw on Nat Geo that Cromagnon and Neanderthal could have been contemporaries and that they met each other. According to this they could have sired two different kinds of humans. I think this may be right. Probably we complement each other.

What do you think?

Answer 1

There are many theories as to the fate of Neanderthals and how they interacted with modern humans.

It is true that both Neanderthals and modern humans existed at one time. There are generally two prevailing hypotheses as to what happened to them.

Hypothesis one is that we were simply smarter than Neanderthals. This means that A) we killed them with our superior weaponry (human spears could be thrown much more efficiently than the larger Neanderthal spears) or B) We simply outcompeted them and they died off or C) we interbred with them and they disappeared into our gene pool. It is possible that what truly happened was a combination of one or all of the above.

There is some contention among scholars as to whether Neanderthals are a separate species from modern humans (Homo sapiens versus Homo neanderthalensis) or if they are simply a subspecies of modern humans (which would make them "Homo sapiens neanderthalensis").

And yes, the Neanderthal genome has been mapped. Type "Neanderthal genome project" into Wikipedia. The results do not give a definite answer as to whether or not humans and Neanderthals interbred, but I myself think it likely.

As for the statement "According to this they could have sired two different kinds of humans," that's pretty much baloney. In fact, the most recent common ancestor of all living humans is probably no less recent than 5,000 years ago - that's not even as far back as prehistoric times. If you're interested in knowing more, you can look up the article "On The Common Ancestors of All Living Humans." by Douglas Rohde. You can read it online in PDF format.

To the above poster (Monarch Butterfly): There are no such things as "races" in anthropology. The word "race" is used to describe subspecies within a population that have a whole gamut of different variations. However, people of different skin colors only have one variation: skin color. Thus, skin color is a clinal, rather than racial, attribute. The idea of race is a cultural construct in the strictest sense. Also, the variation in between separate cultures is very little, and there is far more variation AMONG cultures than there is BETWEEN them. Skin color is as insignificant in determining relatedness as, say, blood type.

Answer 2

It's possible, but there is no evidence that the two species ever interbred.  They're not sure if they could have, due to the "large-X-effect".

Answer 3

Fascinating material!

I have read and heard many times that Cro-Magnon and Neanderthal were contemporaries, but I have also always heard and read that they did NOT crossbreed.

I don't know if they just couldn't - as your other responder suggests - because of the DNA, or if they had some primative equivalent of a cultural taboo against mixing and matching.

Or could it be that they just occupied spaces separated by enough geographic space and natural boundaries that they lived in the same time but without physically encountering eachother?

Yet, if the two species had survived separately to the present day, we would have two distinctly different lines of descent living today.  As it happens, we DO have about 3 or 4 distinctly different races, but how much difference is there between "races" and "species"?

I think it is more probable that one of the two original species was completely wiped out somewhere along the way, and we are descended from the surviving one.  This could have happened with either of the more recent comet impacts - the one in 7640 BC or the one in 3150 BC.  Or perhaps some sort of a species-specific disease took one of them all the way out.  

I do not know if it is true or not, but I seem to recall reading somewhere that even though we look more like the Cro-magnon man, we have more DNA in common with the Neanderthals, so who knows?.

Answer 4

well i think i know a few neanderathol folk...lol!!

no seriously, that makes TOTAL sense!!

Answer 5

There are "scientists" and then there are scientists.

I believe that scientists are mapping the Neander genome. That should tell us whether we are related, the X chromosome notwithstanding.

In any case to expect that modern man did not arrive from the East about 100,000 years ago and competed Neanderthal into extinction would indeed be news that would change our view.

The two species surely did co-exist, so to speak but to prove that Homo Sapien Sapien split directly from Neander is gonna take a lot of proving.

I don't see the time for cortical development.  It is the cortex that seperates us so distinctly from our cousin.