Before I go to town with my interpretation of these topics, I would like to mentioned why this Hugo Award-winning book is one of my favourites. Recommended to me by a science teacher in seventh grade after I expressed an interest in human evolution, the novel got me thinking for the first time about many of the same things I do today - evolutionary biology, religion, the role technology plays in shaping culture and the nature of human cognition. Up until that point in my life, my main concerns were my daily struggles to figure out my identity in the context of my peer group. I was always trying to ascertain my relative position within the elaborate social hierarchy of my school. Once I read Hominids, my self-analysis became much broader in scope. Instead of spending so much time thinking about the minutiae of seventh-grade life, I often found myself deep in thought trying to understand my identity in the context of humanity (which is a much more interesting question in my opinion). Just what does it mean to be a human? I'm still working on that one.
Since the book is approaching 10 years of age, I thought it would be fun to go over some of the details of the trilogy to demonstrate the relevance of the work in 2011. In this first post I'm gonna talk almost exclusively about the paleoanthropological science present in Hominids, Humans, and Hybrids. My next two posts will focus on the technological culture Sawyer has created for the Neanderthals and the role of religion/spirituality in contemporary society, respectively.
Today in 2011, we know a great deal more about the Neanderthals than we did in 2002, though many of the details of their lives remain mysterious. Before we take a look at any Neanderthal stuff in particular, let's take a look at our picture of the human family tree, both as it was in 2002 and today. In 2002, we would have (more or less) considered the following to be the only members of the "Homo" genus:
- Homo rudolfensis
- Homo habilis
- Homo ergaster
- Homo erectus
- Homo heidelbergensis
- Homo neanderthalensis
- Homo sapiens
- Homo gautenengis
- Homo georgicus
- Homo floresiensis (the famous "hobbits")
 | |
| Denisovan tooth |
 |
| Homo floresiensis skull - I think I would have enjoyed the Floresiensis parallax |
The reason I bring up the number of shared base-pairs among modern humans, Neanderthals and Denisovans is that the findings have flown in the face of what Sawyer postulated in Hominids, demonstrating the amount of progress made in paleoanthropology in less than 10 years. At the time of Hominids' publication, it was science fiction (literally) that anyone would be able to perform genetic analysis with such precision. Consider the following excerpt from Hominids, which details the "Vaughan method" of DNA extraction using the PCR (polymerase chain reaction):
In 1994, Mary had made a name for herself recovering genetic material from a 30,000-year-old bear found frozen in Yukon permafrost. And so, two years laters, when the Rheinisches Amt für Bodendenkmalpflege - the agency responsible for archeology in the Rhinelands - decided it wa time to see whether any DNA could be extracted from the most famous fossil of all, the original Neanderthal man, they called on Mary. She'd been dubious: that specimen was desiccated, having never been frozen and - opinions varied - it might be as old as 100,000 years, three times the age of the bear. Still the challenge was irresistible. In June 1996, she'd flown to Bonn, then headed to the Rheinisches Landesmuseum, where the specimen was housed.
The best known part - the browridged skullcap - was on public display, but the rest of the bones were kept in a steel box, within a steel cabinet, inside a room-sized steel vault. Mary was led into the safe by a German bone preparator named Hans. They wore protective plastic suits and surgeons' masks; every precaution had to be taken against contaminating the bones with their own modern DNA. Yes, the original discoverers had doubtless contaminated the bones - but after a century and a half, their unprotected DNA on the surface should have degraded completely.
Mary could only take a very small piece of bone; the priests at Turin guarded their shroud with equal jealousy. Still, it was extraordinarily difficult for both her and Hans - like desecrating a great work of art. Mary found herself wiping away tears as Hans used a goldsmith's saw to cut a semicircular chunk, just a centimeter wide and weighing only three grams, from the right humerus, the best preserved of all the bones.
The hard calcium carbonate in the outer layers of the bone should have afforded some protection for any of the original DNA within. Mary to the specimen back to her lab in Toronto and drilled tiny pieces out of it.
It took five months of painstaking work to extract a 379-nucleotide snippet from the control region of the Neanderthal's mitochondrial DNA. Mary had used the polymerase chain reaction to reproduce millions of copies of the recovered DNA, and she carefully sequenced it. She then checked the corresponding bit of mitochondrial DNA in 1,600 modern humans: Native Canadians, Polynesians, Australians, Africans, Asians and Europeans. Every one of those 1,600 people had at least 371 nucleotides out of those 379 the same; the maximum deviation was just eight nucleotides.
But the Neanderthal DNA had an average of only 352 nucleotides in common with the modern specimens; it deviated by a whopping twenty-seven bases. Mary concluded that her kind of human and Neanderthals must have diverged from each other between 550,000 and 690,000 years ago for their DNA to be so different. In contrast, all modern humans probably shared a common ancestor 150,000 or 200,000 years in the past. Although the half-million-year-plus date for the Neanderthal/modern divergence was much more recent than the split between the genus Homo and its closest relatives, the chimps and bonobos, which occurred five to eight million years ago, it was still far enough back that Mary felt Neanderthals were probably a fully separate species from modern humans, not just a subspecies: Homo neanderthalensis, not Homo sapiens neanderthalensis.
I apologize from the very long excerpt, but I felt cutting anything out of the passage would have been at the expense of context and clarity. As you can see, Sawyer's Neanderthal Parallax operates around the assumption that Neandethals and humans were too genetically different from each other to have interbred and produced fertile offspring. Note that the trilogy explicitly states that the lack of interbreeding between Neanderthals and modern humans is a result of genetic incompatibility. Without spoiling any details, I will add that a major element of the trilogy's plot revolves around the impossibility of combining human and Neanderthal genomes without sophisticated technological intervention. Just go read the books!
Recently, however, the Net has been buzzing with headlines proclaiming that 1-4% of our genomes (sort of - read on) comes from Neanderthals. Though Sawyer made a well-reasoned, well-educated conjecture about the compatibility of Neanderthal and Homo sapiens sapiens genetic material, it turns out both that Neanderthal/modern human interbreeding did indeed occur and that children of such couplings were fully capable of reproduction (without advanced technological intervention). In fact, it's not really even appropriate to say "Neanderthal/modern human breeding" since some modern humans are in fact, Neanderthals, at least in the strictest sense of the word.
These findings have drastically reshaped the way we have to think about the chronology of human evolution. I should have specified earlier that the 1-4% of DNA that is Neanderthal only seems to be present in populations other than those of sub-Saharan Africa. Interestingly, this amount of Neanderthal present in modern populations is equally dispersed amongst people from Europe and Asia, meaning there is equal amounts of Neanderthal DNA in a French person as there is in a Chinese person. This suggests that interbreeding occurred before we had diverged into the many racial groups which span the area from western Europe to the far east, around 80 000 years ago. Richard Green et al. have presented four possible scenarios which describe the connection between modern humans and Neanderthals, but write that "gene flow between Neandertals and the ancestors of all non-Africans" to be the most consistent with their data. You can see the paper here and read the abstract here. Links are also on the bottom.
 |
| Four scenarios presented by Green et al. They consider Scenario 3 to be most consistent with their data |
The real interesting question now is what exactly that 1-4% of Neanderthal DNA does, if anything. There is some exciting evidence to show that the transfer of certain human leukocyte antigen (HLA) alleles, presented by Peter Parham. The HLA system plays a major role in the human immune system, and the basic gist of Parham's hypothesis is that by acquiring HLA alleles from Neanderthals after hundreds of thousands of years of isolation and natural selection, modern humans were able to give their immune systems a boost to protect against dangerous pathogens localised to the new environments which were being explored by our ancestors.
This is an exciting idea and raises many scientific and philosophical questions. John Hawks disagrees that the common HLA alleles are definitive signs of interbreeding, but whatever the case, the fact that we are able to find so much info about the Neanderthal genome is very exciting and could provide us with great insight into the history of our species' great success.
Some readers might feel that the fact that the plot of Hominids doesn't hold up to the contemporary science detracts from the book, but I disagree. First of all, most science fiction does not stand the test of time and works that were taken very seriously as predictions of the future now seem slightly ridiculous in retrospect. Consider the level of technological sophistication supposedly present around the turn of the century in Clarke's 2001: A Space Odyssey. The fact that the science in the book doesn't correspond with real-world findings is only to be expected (eventually) and doesn't detract from the book or make it irrelevant. Even with these little inconsistencies, Hominids is still probably the most paleoanthropologically informative novel you will ever read.
A second and more important reason that Hominids is still relevant is the social commentary. As I mentioned before, Robert J. Sawyer has often commented that science fiction is really about the present as much as it is about the future. With this in mind I think an examination of the culture he's created in Hominids provides valuable insight into the possible consequences of several current trends, such as global access to information, the role of spirituality in a increasingly secular world, the merits of a technocratic society and most saliently, the lack of privacy that comes along with being connected to a global network at all times. Some people believe the lack of privacy is an inevitability of technological progress, exemplified by Scott McNealy's reality check "You have zero privacy anyway. Get over it." Others think that the key to keeping the Internet "free" (speech, not beer. That would be nice though) is to promote personal privacy, anonymity and decentralisation. These are the kinds of people who would sooner keep their data in a vault than in "the cloud" (an expression I despise).
In my next post I'm going to talk about the Neanderthal world Sawyer has created and discuss whether or not the kind of society he presents is realistic, feasible or even desirable in our world. Though Sawyer was careful to not make the Neanderthal world "perfect", his Neanderthal society is a pretty thinly-veiled metaphor for what I assume to be Sawyer's personal vision of a technological Utopia. In a third and final post about the Neanderthal Parallax, I'll also take a stab at Sawyer's vision of the place of human spirituality and religion in a technological society. It seems we may have a lot to learn from cavemen.
References:
Robert J. Sawyer's webpage - www.sfwriter.com
Richard Green et al. "A Draft Sequence of the Neandertal Genome"
No comments:
Post a Comment