Replies to This Discussion

Permalink Reply by Chris Dodds on August 30, 2012 at 6:36pm

Wait, if Neanderthals and modern human interbred, wouldn't their offspring be infertile like a Liger?  I thought that hybrids were always infertile, or am I just mistaken?

Permalink Reply by John Jubinsky on August 30, 2012 at 10:15pm

The offspring are not always infertile. Certainly significantly different species of dogs when interbred can produce fertile offspring.  I suppose it depends on how different the species are. Per the article below:

 

....A small amount of that genetic mingling survives in "non-Africans" today: Neanderthals didn't live in Africa, which is why sub-Saharan African populations have no trace of Neanderthal DNA....

 

http://www.newscientist.com/article/dn18869-neanderthal-genome-reve... 

Permalink Reply by Chris Dodds on August 30, 2012 at 10:45pm

Well, I guess if the two species are closely related enough, such as when they're insame genus and share a very recent common ancestry (as in Homo Sapiens and Homo Neanderthalensis), than hybrids of the two specie could be fertile.  But back to the above article, where does this place the Denisovans on the human family tree?  Are they an entirely new species or rather a subspecies of an existing one, such as Neanderthals

Permalink Reply by John Jubinsky on August 31, 2012 at 5:23am

My understanding is that they are supposed to be a distinct species but closely related to Neanderthal. My understanding is that they were more closely related to Neanderthal than to us. However, some of their genes are supposed to exist in some of us and so it seems that they were closely related enough to us to interbreed with us.

Permalink Reply by michele ricketts on September 16, 2012 at 9:32am

$ reading about this they say a nethandral woman couldn't pass her micocochondrial Dna to homo sapiens
also homo.sapien females had difficulty giving birth to a nethandral baby as her birth canal was not big enough to breach a nethandral baby since nethandrals were bigger and stronger ( and hairier)
That said nethandral females inpregnated by a male could.

Permalink Reply by John Jubinsky on September 16, 2012 at 12:19pm

It could very well be true that female Neanderthals had difficulty passing their X chromosomes to hybrid offspring involving modern partners because, according to the article of this discussion, Denisovans (which were closely related to Neanderthals) produced a disproportionately low X chromosome gene pool in our population. Per the article:

 

Intriguingly, comparing the X chromosome, which is passed down by females, to the rest of the genome, which is passed down equally in males and females, revealed "there is substantially less Denisovan genetic material in New Guinea on the X chromosome than there is on the rest of the genome,"researcher David Reich at Harvard Medical School in Boston told LiveScience. One possible explanation "is that the Denisovan gene flow into modern humans was mediated primarily by male Denisovans mixing with female modern humans," Reich said. "Another possible explanation is that actually there was natural selection to remove genetic material on the X chromosome that came from Denisovans once that entered the modern human population, perhaps because it caused problems for the people who carried it."

 

 

 

Permalink Reply by michele ricketts on September 16, 2012 at 3:42pm

Sorry ignore the first paragraph/ sentence of my first reply;got interrupted editing that post. There is no lineage traceable through female micochondia as all that left from nethandrals is sequences buried in Dna as fragments within our Dna. That turns up as 4% of our own.
It is said that nethandrals did not have as evolved speech as homo.sapiens whether a brain thing or/and under developed vocal chords.So the off-spring had some disposition to be dumber.
Fascinating stuff. It was alarming once to come across a strong man with a REALLY hairy back in a swimming pool. ( joke !)

Permalink Reply by Scott McGreal on August 30, 2012 at 11:46pm

I have read that when considering extinct races it is difficult to set a clear demarcation on whether they are a distinctly different species or not. If humans and Neanderthals interbred it suggests that differences between the two involved a genetic distance that while noticeable was not insurmountable.

Regarding skin colour, I have read that some researchers think that fair skin, hair and eye colour evolved fairly recently, say in the last 30,000 years or less. This paper argues that variations in hair and eye colour among Europeans were mainly due to sexual selection, as people with say blonde hair and green or blue eyes had a distinctive appearance that made them particularly attractive.

Permalink Reply by John Jubinsky on August 31, 2012 at 5:29am

This might be true because native Asians of Northern Siberia nonetheless have dark hair and eyes.  That is, the cold climate there did not induce lighter hair and eyes. However, people with lighter hair and eyes do have the advantage in a cold climate of getting more Vitamin D from the sun. Therefore, this might also have had something to do with its occurrence in Northern Europe. However, again this did not induce lighter hair and eyes in Northern Siberia.

Permalink Reply by Joseph P on August 31, 2012 at 7:51am

Yeah, that's what people don't understand, when they only learned about Evolution from their fundamentalist preachers who have an agenda to keep them ignorant.  The same gene that saves your life in one climate will kill you in another climate.  There are very few variances in the human genome that are 'better' in every situation.

Dark skin decreases your chances of skin cancer, in a more equatorial climate.  Pale skin decreases your chances of dying of rickets, in a more polar climate.

Permalink Reply by michele ricketts on September 16, 2012 at 3:53pm

Thought it appeared 10 000 years ago. Right about evolved as more attractive because it is not initially inked with whiter skin and its tendency to go with blue eyes to access vitamin D from cloudier skies in Nordic places.
Though advantageous to vitamin D from the sun.

Permalink Reply by Ant Mac on September 13, 2012 at 2:09am

This is a very interesting topic. Let me first say I am not aware enough of the science to venture on using the correct terms. I probably understand them, but won't risk using them, as a layman.

 

However, when you consider the visual differences between the present "races" and the fact that this means very little at all, if anything at all, to the viability of our off-spring, and then you consider what we know about the visual differences of Neanderthals and Cro-magnons, it makes one wonder where exactly you can draw a iine between populations that were contemporary.

 

If they could breed together, could they be considered separate species at all?. Are they not just one species wildly variant in superficial ways?. It is interesting, and I wish I had more time to learn about it in depth.

 

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