Genetics is science still in its infancy. The structure of DNA was only identified in the 1950’s, and the human genome was mapped in 2003. Compare that to the study of physics or chemistry where the key building blocks of our understanding have been in place much longer. A lot of what we thought we knew about genetics ten years ago now is considered out of date and inaccurate; what we think in 20 years of what we think we know now, who can say? As such this is more a progress report on genetics in 2016 than a definitive survey of the science, comprehensive though it is.
I have always been fascinated by the puzzle that we all have increasing numbers of great grand parents as you go back each generation, but that the total human population in much higher now than it has ever been. Rutherford calculates that it you go back to the eighth century we will each have required 137,438,953,472 people in our family tree. I make that about 33 generations, but of course many times more than the number of people who have ever lived. It follows that family trees are a misleading presentation of our genealogy. There must be many points across our family history were the lines cross and blend. “What this means is that pedigrees begin to fold in on themselves a few generations back, and become less arboreal, and more mesh or web-like”. Rutherford expresses this point by looking at the genealogy of some of the Royal families of Europe. Charles 2nd of Spain should have had 62 ancestors in his preceding six generations, (2 parents + 4 grandparents + 8 great grand parents and so on). In fact he had only 32 – many of his great aunts were also his great grandmothers, for example. Go back another two generations and instead of over 250 ancestors he had 82. This is obviously an extreme example caused by the shallow gene pool from which the royal families chose their partners, but go back far enough and the same pattern would be seen in all our families.
The other riddle that Rutherford answers definitively here is whether, as is often suggested, we are all eventually related to Attila the Hun. The short answer is if you go back around ten centuries or so then we all share some genetic material from everyone who lived at that point. This is obviously highly counter-intuitive, but Rutherford demonstrates it with precision and statistics. I would struggle to repeat the analysis for myself – it’s complicated – but I take some comfort from knowing where to find it if I need it!
This is an eclectic look at the state of genetics today, including issues as diverse as why the distribution of wet and dry ear wax in humans suggests that the people of South Korea might be the least smelly on earth; why the idea of a Danish Viking conquest of the British Isles involving rape and pillage is not borne out by a genetic legacy; and why monoamine oxidase A, the so-called “warrior gene”, ought not to be a valid defence in criminal trials. Rutherford charts our progression as a species from out of Africa, using evidence provided by ancient DNA. A toe bone of a Neanderthal who died 50,000 years ago in the Siberian reveals our ancestors appetite to mate with other humanoids now extinct, explaining why we all have a little caveman DNA in our genome.
Genetics is complex, and there were pages in the book were my non-scientific eyes glazed over, there’s no point in denying otherwise, however accessible this book was intended to be. The analysis of whether race is a genetic characteristic, or whether it actually exists or not, was a case in point. I think Rutherford concludes that it both does and does not, but I would need to check. The relationship of disease to genetic is equally complex. You start out by looking at the more obvious inherited illnesses such as Tay-Sachs disease or sickle cell anemia, and think yep, that makes sense. But once you start looking at more complex conditions and characteristics, even those most obviously inherited such as height, tracing the precise role our genes play in this process has proven elusive. Or that was what I understood Rutherford to be saying anyway!
I know a little more about genetics than I knew last week, which has got to be a good thing. But I must admit I will return to the comfort of fiction in the coming days with a small sense of relief.