Re: neanderthals and us
Posted by: poetscientistdrinker
Date: March 28, 2003 12:48PM
Good question, and there's good and bad news. The bad news is that I'm currently 100 miles away from my notes on human origins and Quaternary environments, the good news is that I can remember a shed-load and I'm sat in a university library. This of course means that I can be a terrible smart-arse, so I'm going to indulge myself.
Going back as far as Neanderthals:
'Thals were around up until as recently as 30,000 years before the present, although there is evidence from the Pyrenees of them hanging on a bit longer than that, although this is the subject of much debate. They probably evolved atb the same time as recognisably modern humans about 150,000 years before present. One area of intesne debate is whether they were a sub-species of Homo sapiens or a seperate species Homo neanderthalensis. As with all these debates, it depends on your personal definition of species. mitochondrial dna supports the seperate species theory, but the significance of this is again debatable.
There is evidence that neanderthal genes persist in current populations, although the majority view is they aren't direct ancestors of modern people. The evidence includes caucasian males having a ridge of bone above the eye-sockets (feel it yourself) and it is also postulated that red hair and freckles ,ay also be a neanderthal hangover from 'Thal populations breeding into the gene pool in Europe. Again, there isn't much way of telling decisively, although I confess that it is an attractive idea.
One major difference seems to have been the hyloid bone, a small bone in the throat that affects speech. The postion of this in 'Thals seems to suggest that their voice box was not as advanced as ours, reducing the range of sounds available. The influence of this on language is debatable - sign language is perfectly possibly for those who are deaf, for example.
Whatever you believe about seperate species, the evidence all points to them being very similar to modern humans in physiology. They may have been marginally more adapted for the cold, but then this wouldn't mean they couldn't cope with modern conditions. For example, inuits are adapted for the cold- especially their noses, yet have no problem with climate in any other part of the world.
Bearing in mind modern humans were also in Europe during the last glacial period (the Devensian, dontcha know) you have to assume that there hasn't really been that much change. Especially when you look at some of the coditions during that period. For example, during the early part of the last glaciation, there is evidence that summer temperatures were higher than the modern day. No evidence from ice cores or any other source show a significant change in concentrations of oxygen, although CO2 levels may have changed this change is less than the change through moving from a crowded room to the open air in modern life.
So, basically, 'Thals would have no problem surviving in modern climates, and indeed had survived millennia in similar environments. Similarly, there is no problem with modern humans flying from the British Isles to the tropics - a far bigger climatic change. This seems to suggest that there would be no problem with us travelling in time to different climates either.
Further back than 'Thals... some issues.
Climatic conditions in the deep past, however, may be very very different to the modern day. There is some evidence that the atmosphere in the Carboniferous period may have been much more oxygen rich. This may not be a problem for us going back in time then, but would be a problem if you tried to regenerate a giant dragonfly from the time - it simply wouldn't be able to get enough oxygen to stay alive. However this is a specific case, and generally the climate would be the least of the problems. Certainly the range of animals re-engineered in the TN books have all been alive during conditions similar to todays. Mammoths, interestingly, survived both the worst conditions of the Devensian glaciation and the warmest parts of the Ipswichian interglacial before it. All the evidence is that they would have thrived under current conditions. Unfortunately there was a short burst (<500 years) of low summer temperatures that may have finished them off along with hunting. Much of the ice ages had a higher seasonality then today - average temperatures were lower, but often summers were warmer.
As an extra aside, if Mr Ff decided to bring back the Irish Elk (actually a giant red deer), then I would have an excuse to inform you all that it went extinct not due to its huge antlers (which were as big as you'd expect for a deer that size) but due to the growth of forests, which it couldn't survive in due to its bulk. Mammoths may also have had a problem with this happening, although it has been argued it was the mammoths going extinct that allowed the forests to spread.
The real problems with re-engineering species...
The real problem, of course, is not the physiology of extinct creatures, it's the technical problems. Firstly, DNA is a remarkably tricky thing to preserve. It is degraded by light, enzymes in the body, heat, time and radiation. Basically, even getting a whole strand out of a living cell is ridiculously hard, and out of something dead makes it even harder. The best bet would be to get it out of something frozen - hence the excitement over possibly finding frozen mammoths in Siberia. Filling in the gaps with other DNA may be possible, but would require a greater understanding of what DNA is vital for development than we currently have. For example, nobody can explain junk DNA convincingly. It does something, or it would be too costly to keep replicating it - we just don't know what. It may be that it would be even more costly to cut it out, but this isn't terribly satisfactory, as different species have different amounts. There's also the problem that chromosomes alter as you age - telomeres shorten, for one thing. This is what may have given Dolly premature arthritis.
Once you have the DNA, getting an egg to accept it is another thing. Dolly the sheep required hundreds of attempts, and that was for an egg from the same species. With extinct species, you have to use a close relative, and this presents problems. For example, some of the instructions for the development of an organism come from the contents of the egg itself, other information comes from DNA in the mitochondria, which have evolved in step with the chromosomes for each species.
These are only the start of the problems, and having done some work with dna manipulation, I can assure you they're the least of them. Just getting a sequence of dna to enter the genome in the right way is damned hard...
One final thing - don't make the mistake that 'pre-historic' means 'very old'. Pre-historic means before writing, basically, and covers different periods of time inn different regions of the world. Pre-historic in Britain means about 2,200 years, in the middle east we're talking 6,000, in the Americas it could be argued that pre-historic is about 550 years ago! By this reckoning, pre-historic covers a range of a couple of billion years. Obviously something from that far back may be very different to modern organisms, something from 30,000 years ago is going to be very, very similar.
Thanks for the intellectual work out - Any questions from the audience?
Post Edited (03-28-03 13:58)
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