‘Know then thyself, presume not God to scan; the proper study of Mankind is Man,” sang Alexander Pope. And he continues with perhaps the most eloquent description of our fallen natures in the English language. But he didn’t have to contend with scientific studies which come in threes, as I have to do. While I have no difficulty in squaring man’s unique nature with evolution, new information requires new consideration.
The first of my three is our cousin, the common fly. You might think that the central brain region of the fly we swatted on the windowpane this morning would be very different from our own. But in fact the basic ganglia of humans and the central complex of the fly’s brain turn out to have a similar genetic origin and to operate in similar ways. The same neural mechanisms control internal stimuli such as hunger and sleep, and external stimuli such as ambient light or temperature. Even the defects in our brains which can cause disabilities such as schizophrenia or neurodegeneration occur in similar ways.
These characteristics are so alike that scientists tell us that studies of these distant cousins may well help us to understand, and perhaps remedy, human disease. Increasingly, problem conditions are being tackled through the genetic route.
Not everyone will welcome the confirmation of our evolutionary connection to other living species, although the evidence on a larger scale – such as the basic body plan of lower animals – tells us that it must be so. Why did God set about creation in such an indirect way? Blest if I know. And blest if I don’t. I just marvel.
Last year a new set of fossils from Australopithecus Sediba were discovered and Science has just published some studies of this ancestor of ours who lived around the time of the first in the Homo line about two million years ago.
Sediba is of great interest because of its mix of ape and human features – good evidence on an early link to an ancestor. And an important aspect of this evidence is how well a species was adapted to walking: Sediba has a human-like pelvis but a chimpanzee-like foot. The inference is drawn that he (and she) spent more time in the trees, and this is supported by the nature of the arms, but not by the hands which are more human-like. The rib cage was ape-like, and he had a strong and flexible spine. The scientists conclude that “everywhere we look in these skeletons, from the jaws on down to the feet, we see evidence of the transition from australopith to Homo; everywhere we see evidence of evolution”.
I have taken a personal interest in the work of early Homo because I have a granddaughter studying such things at university. I have been struck, on one hand, by the enormous amount of information discovered and, on the other, at its provisional nature – since fossil remains must be only a tiny sample of our distant ancestry. It is a fast-moving field and I take pleasure in keeping my granddaughter slightly ahead of her tutors.
The “three-parent baby” is back again. Our Human Fertilisation and Embryology Authority is seeking legal change to enable experiments on human blastocysts (the cellular structure forming about five days after fertilisation). You may remember that the procedure makes use of a third parent’s mitochondrial DNA to replace the faulty version. Existing work shows good progress but there are still a number of difficulties, and so much more experimentation is required.
There are two issues here. The methods envisaged require that the egg and its fertilisation take place outside the reproductive tract – so clearly moral issues concerning the dignity of human reproduction arise. Perhaps of more gravity is the number of fertilised eggs which will inevitably be destroyed. The Catholic position prohibits this. Moreover the prospect of three parents per human is one that sharply raises the ecclesiastical eyebrow. On the other hand, it is clear that faulty mitochondria can cause alarming diseases – from mental impairment to blindness and death. Mitochondrial DNA contributes 37 genes compared with more than 20,000 in the nuclear DNA. Moreover, where nuclear DNA defines personal characteristics, mitochondrial DNA does not. We all inherit our maternal DNA, with no change other than incidental mutations. While technically three parents are involved, the practical reality is that there are only the two unique parents. There might, of course, be legal considerations, although I find it hard to believe that the gift of mitochondrial DNA would form a basis for any parental rights.
Here, with permission, I reproduce a comment made on SecondSight Blog, when this question was first discussed: “This benefit may be a short-term one, and open the way to an acceptance that we are free to do anything we wish with the process of procreation. Imagine the possibility of producing new human beings from, say, skin cells, which have been reprogrammed. Or perhaps producing a hybrid from mating human DNA with animal DNA. Such procedures may look both grotesque and unlikely today. But they are no more grotesque and unlikely than this current procedure would have looked a few years back.”
Wisely said, I think. But it can do no harm to look again, in the light of scientific knowledge and scientific potential, at what we teach – in order to confirm our views and to explain in ways which make our principles clear to both the public and the regulators.
Nervous system of flies.
New Scientist 23 March 2013