When Darwin died a hundred years ago; he could reasonably have said, ‘Après moi, le déluge,’ because we are still awash with books and ideas for, against and about him. The issue is intellectually enthralling, moves rapidly, and is of practical importance. The Monkey Puzzle is about the origin of man, and, in particular, about the date when the line which led to us separated from that which led to chimpanzees and gorillas. There is a debate in progress as to whether this separation occurred four or 20 million years ago.
You could easily persuade me that my grandmother was a chimpanzee. I do not recall her saying anything, nor do I remember her making tools or fire. I do remember her giving me fast clouts about the ears. This ability to move our arms freely in all directions we share with the apes in memory of our mutual days swinging in the trees. It is called brachiation, and is one of the many large and small features which we have in common with apes. My parents assured me that my grandmother was a dragon, but I have since learnt that these are mythical beasts, and so I remain open to suggestions about grandmother’s nature. This book tells me that she was almost certainly a member of our species, but I retain a lingering doubt. The authors come from astrophysics and biology. They write with great clarity, and belong to that excellent school of science writers, the New Scientist.
What are the aspects of science to which a general reader should pay attention? It is not enough to say that science is an important part of our general culture, because the same can be said of Chinese literature or watercolours. I am not even certain that evidence about the origin of man should necessarily attract your attention. It so happens that the matters presented by these authors are worthy of attention for reasons which go beyond the particular arguments. In the first place, schools of serious scientists reach quite different conclusions from differing studies directed at the same question. Here you have a chance to consider the nature of scientific thinking and of scientific evidence. Spice is added by the evident disdain with which the two main schools address each other. Since our culture tends to be dominated by a respect for science, it is interesting to read about a scientific conflict, especially since the question can only be solved by extrapolation and not by direct evidence. We do not yet envisage a time machine which would allow us to go back to investigate the origin of man on the spot. Therefore we are inevitably left with that special form of guesswork, hypotheses. These have rules and predictions and probabilities, and we all need to be skilled at handling them whether we are poets or peasants.
A second reason for recommending this book to the general reader is more urgent. It has to do with the question of exactly what constitutes the inherent differences between species and between individuals. These differences are becoming precisely defined in terms of molecular structure, and the authors give us a brief survey of molecular genetics. This field affects our society in two immediate ways. One way relates to the possibilities for transplantation of healthy tissue to replace sick tissue. When blood transfusion was first tried by Boyle in 1660, he used lambs’ blood, chosen with disastrous consequences because of the lamb of God. Now molecular biology has discovered quite a lot about how our bodies recognise even very subtle differences. This allows a search to be made for compatible tissue, or for ways to suppress the body’s mechanism for rejecting the foreign implant. The future of transplantation is much more interesting than the present relatively crude plumbing operations of sewing in whole organs, hearts, kidneys, livers, and will surely extend to the transplantation of single cells and parts of cells. This leads to the second way in which society is affected. Genetic engineering is beginning. It is now becoming possible to change the genetic nature of bacteria and plants so that they produce valuable substances. For example, insulin is made in the pancreas but is so deficient in millions of diabetics that they require daily injections. The insulin they use is extracted by tedious and expensive methods from the pancreas of millions of pigs. Genetic orders have been inserted into bacteria, which turn into factories producing unlimited quantities of exact copies of human insulin. We are at the beginning of a type of revolution.
The classical evidence on the origin of man depends on fossils, and the discovery of this evidence depends on a chain of highly unlikely strokes of luck. The corpse must not be demolished; fossilisation requires just the right weather conditions for millennia; the rocks in which the fossil lies must be datable; and finally the fossil has to be discovered. Given this series of improbabilities, it is not surprising that the total amount of evidence about our immediate ancestors fits easily into a few shoe boxes, and that there are huge gaps of millions of years which are crossed by clever or crazy extrapolations. New evidence continues to appear and often requires a radical change in the suggested family tree. One of the serious problems in handling this evidence is the question of whether a particular specimen is a link between two other types or is a dead end. It cannot be told if Neanderthal man died out or was stamped out by us or merged with us.
An entirely different type of evidence is now brought to bear on the question and is perhaps too forcefully propagandised in this book. We share with near and distant relatives certain types of molecule. For example, we all have red blood coloured by haemoglobin, but there are very slight differences between these molecules in different species. It is now possible to define exactly these differences and their causes, as a result of the work of such men as Sanger. He received two Nobel Prizes, one for showing how to analyse the sequence of units which make up a protein, and one for the analysis of the code sequence in DNA, which is the genetic molecule which contains the detailed orders for making the proteins. Pauling, who also received two Nobel Prizes (one was for Peace), made a suggestion for ways in which the small differences between molecules in the same family could be used to date the relative ages of the species. The DNA molecules are being continually duplicated and handed on from generation to generation. At every duplication there is a slight chance of a slight error, a misprint. This error will then be faithfully handed on to the next generation just as a printing press perpetuates the typographer’s error. It is proposed that the chance of error is rare but equal at each duplication. Therefore errors would occur on average every so many generations. Therefore counting up the errors of duplication between an old species and a new one would give a clock count of the age difference. This proposal was taken up by scientists – particularly by Sarich and Wilson from Berkeley, who are made into the heroes of this book (probably to their embarrassment). They conclude that man’s line separated from the chimp-gorilla line a mere four million years ago, whereas paleontologists tend to conclude that this event took place 20 million years ago.
The arguments between the two schools are fascinating, but I suspect the reliability of both. The paleontologists are short of fossils and long on guesswork. The molecular clock needs its reliability questioning. In this book, it is likened to the radioactive decay methods such as carbon dating which are used so successfully to give ages to plants and to rocks. But there is a striking difference between these two clocks. Radioactive decay proceeds willynilly in an absolutely predictable fashion. However, biological molecular errors cannot accumulate in the same inevitable fashion. For example, normal chimp and normal human haemoglobin differ by only one unit, and this difference may well be quite inconsequential. Meanwhile some humans have another type of haemoglobin differing by another single unit. This difference has huge consequences. On the one hand, it gives its possessor resistance to malaria, and on the other hand it produces the disease sickle cell anaemia. This genetic defect wipes itself out in parts of the world where there is no malaria but has a positive selection advantage in malarial areas such as West Africa. This example shows that the ticks and tocks of the molecular clock may perhaps occur regularly, but that they are then accepted or thrown away by a selection process. That selection is one of the crucial factors in Darwinian evolution, but it makes for a most unreliable clock. Enormously complex organisms such as man or apes have achieved an extraordinary freedom to withstand the slings and arrows of their external environment. They have done this by building a very precise, delicately structured internal environment which cannot absorb most genetic errors. This is likely to make an error-accumulating clock less and less reliable in more complex animals. Similarly, the introduction of a chunk of genetic material happily converts a bacillus to the production of completely novel protein while the same change would almost certainly demolish us. The last chapter of this book should not be missed since it is likely to cause a riot in the Antipodes. Tubes of Foster’s will be raised and ‘Right on, sport!’ will be shouted when they read that the most recent evidence can be interpreted as suggesting that Homo sapiens originated in Australia rather than Africa. Before they let rip in an orgy of Pommie-bashing I should warn them that yet another rival school places our nursery in India.
The Monkey Puzzle is wild, gossipy and lots of fun. If the reader prefers a sober consideration of these issues, he should read Darwin Defended by Michael Ruse, a professor of the history and philosophy of biology. We can now move to a section of the library which could be called ‘The Descent of Authors who write on the Descent of Man’. Ms Elaine Morgan is a fe-fi-fo-fuminist who writes books on the origin of the hu-person race. She is famous for her Descent of Woman. Here, in The Aquatic Ape, she takes rather seriously what I had always assumed to be one of these elaborate joke fantasies grown in Camford common rooms when they tire of discussing their mortgage problems. In 1960, Sir Alister Hardy, professor of zoology, proposed that man, in his long journey from the trees to Oxford University, had diverted into the water for some crucial developments. What better place to learn to stand on legs without falling down? Shorten the toes and web them for swimming. Get rid of hair except for mother, who provides long hair for the child to hang onto. Develop blubber under the skin for insulation. Cry tears like the crocodiles and unlike the monkeys. Diving reflexes for babies. Move the vagina ventrally so that copulation can take place belly to belly to avoid the drowning of the mate which would occur in using the position popular among our simian relatives. What a marvellous idea – and best of all, no chance of finding any evidence to refute it. If man died at sea, the marine organisms would not waste a good dinner to provide fossil evidence. If swimming man was chucking rocks at the birds, leaving no tern unstoned, we would have little chance of finding his artefacts. All great stuff, and certainly more attractive than the popular untested, untestable theory of man climbing down from the trees and kitting himself out with the anatomy to become the great plains hunter while the little woman cowered in a cave with the kids.
There is, however, another theory: that man derives from a process of prolonged infancy called neoteny. This can be used to explain some of the anatomical features – lack of hair, large head, ventral vagina etc. Perhaps more interestingly, it could prolong the period of learning, of dependence and of socialisation which is characteristic of the very young animal. Neoteny is not just another candidate among a plethora of untestable ideas. There are certain genetic constraints in man’s emergence. One of them is the relatively short time available, and the other is the fragility of our genetic structure. This means that a theory which entails minimal genetic rearrangement with maximal consequences is a more acceptable theory. Many genes control rates of production and it is not unlikely that a very small gene change could induce neoteny by slowing the rate of development. An exciting period like this is full of doubts, debates and conflicting interpretations which make a rich intellectual feast. Of course, there are carrion birds hopping around the edge of the banquet table in pursuit of the scraps. A report on this aspect of the situation is contained in the last of these books. Before the reader agrees with the publisher that it shows Darwin under ‘massive assault’ I recommend the other books first.