There’s two technologies that exist that I suspect might produce human-animal hybrids unintentionally, though I admit I’m not a geneticist and don’t have a scientifically informed opinion.
The first is in vitro fertilization with animal cell co-culture. What happens with this is that an embryo is grown with cells from an animal cell line, such as Buffalo rat liver cells or African green monkey kidney cells. Is it possible that animal DNA (such as infectious endogenous retroviruses) could become integrated into the DNA of the embryo and thus produce a hybrid of man and beast?
The second is gene therapy. Viral vectors for gene therapy are often (usually?) contaminated with endogenous retroviruses from the animals the virus is associated with. For example, mouse leukemia virus vectors often contain mouse endogenous retroviruses. These vectors, when introduced into the human body, go everywhere, including the gonads. Do you think it’s possible that children have already been born who were produced from gametes modified by such a vector, or is that highly unlikely?
Both of these technologies have been in use since about 1990 (though animal co-culture is rarely done today), so there’s been thousands of chances for this to have happened over the past 27 years.
Would a human with a bit of randomly inserted mouse, rat or monkey DNA in their chromosomes meaningfully be “part mouse/rat” or “part monkey”, or would it not really make any difference?
Thanks to retroviruses transferring genes between species humans have* always* had non-human DNA in them. Retroviruses write themselves into the DNA of their hosts and cause it to produce new copies of themselves; but they are sloppy, and often bring along bits and pieces of the host’s genetic information along with them.
I hear this quoted all the time along with 50% overlap with yeast. But if we’re 98% the same as chimps then how can they say we have 2-5% contribution from Neandertals? Presumably a large portion of the common-with-chimp was also in Neandertals.
Both modern humans and Neanderthals are descended from chimps, but at some point the two groups split off. And then at some later point, they interbred. (And similarly with the Denisovans.) So while both modern humans and Neanderthals share the majority of our genomes with chimps, we modern humans have some DNA that went through the Neanderthal branch and got a little tweaking there before coming back to us.
If the Neanderthals had survived, doubtless they would have inherited a fraction of their DNA from us as well.
I understand that, but 98% + 5% = 103%. Apparently something is coming form both routes. But if it was in chimps how can we know it came from Neandertals rather than direct.
We’ve had pig skin grafts for burns {Chicago Tribune – June 1967} for some time now … this isn’t exactly what the OP is asking but I think it relates … we generally don’t call these burn victims “pig/humans” or say they are “part pig” … they’re human with a pig skin graft is all …
Easy, because we know what chimp DNA looks like and what Neanderthal DNA looks like, so they can disregard what’s in common between all 3 and look at what remains to see what’s in common, which is apparently 2-5%.
The math doesn’t quite add up, but I think that’s more than likely reporter ignorance than academic stupidity. It could be something like “Of the 2% of the genome that’s NOT shared in common with chimps and Neanderthals, up to 5% is in common with Neanderthals” and a reporter wrote it up in such a way that makes it sound like it adds up to 103%.
Humans, neanderthals and chimps are descended from a common ancestor, humans aren’t descended from chimps. 5% of our species-specific DNA comes from Neanderthal ancestors, give or take.
Yes, sorry, I was oversimplifying to the point of being wrong… let us say the last common ancestor, then.
Actually, what’s happening is that we are comparing numbers derived from two different definitions.
Looking purely at the sequence, ~98% of the modern human genome is identical to that of extant chimp populations.
For the Neanderthal %, the mixture models are probabilistic; based on allele frequencies in modern humans, Neanderthals, and chips, we think that ~2-4% of the modern human genome is derived from Neanderthals, even though most of that DNA sequence is still identical between modern humans and extant chimp populations. (Note that this completely ignores selection events acting since the mixture happened, which may have affected the final allele frequencies.)
For an analogy, imagine you had a pitcher of fruit drink containing 2% apple juice and 98% water, and another pitcher of fruit drink containing 2% grape juice and 98% water. If you mix 980 ml of the apple drink with 20 ml of the grape drink, the result is still 98% water, but 2% of that water came from the grape-flavored pitcher, even though those water molecules are identical to the ones that came from the apple-flavored pitcher.
From a different point of view, some heart valve replacements use porcine or bovine tissue. I know the animal tissue is treated before implantation but perhaps it still contains animal DNA?
Well as far as gene therapy is concerned the answer is probably no. To my knowledge the retroviral and lentiviral vectors are produced in human cells from either packaging cell lines derived from human embryonic kidney cells or from transfection of these cells with plasmid constructs to make the virus. This would mean that we know exactly what genetic sequences are contained in the virus and, if they pick up any random DNA sequences during production, these sequences would be human derived.