12.06.09
Evolution solved: Wallace’s breakthrough
From Roy Davies The Darwin Conspiracy
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This account of the final stage of Wallace’s discovery of what is now called Darwinism is touching, and it is important to grasp that arriving at this was beyond Darwin’s ability, working alone.
This is the final piece in what he got from the so-called Ternate letter, building on the previous Wallace letters.
CHAPTER 24
Evolution solved
BACK IN the Malay Archipelago, Wallace had been thinking about food supplies, human existence and human species for almost a year. One day, he noticed islanders carrying their abundant burdens of rice and sago along the narrow path between two villages on the island of Gilolo, the most north-easterly of the Spice Islands.
When he had last written to Darwin, his question about whether Darwin would treat the subject of man in the book he was writing had not been idle. Wallace had become fascinated by man. Was every tribe in existence a different species? Were tribes varieties? Had extinction had the same effect on man as it had had on every other species?
He had come to Gilolo from the nearby island of Ternate to seek exciting new specimens and species, but it was the human tribes of Gilolo that absorbed Wallace’s attention. He carefully noted everything he could about the people he had observed in the village of Dodinga: ‘The village was entirely occupied by Ternate men, who are malays with an occasional admixture of papuan blood… The true indigenes of Gilolo [Papuans] live on the eastern coast or in the interior’.1
A few weeks later, he wrote:
The natives of this large & almost unknown island were examined by me with much interest, as they would help to determine whether, independent of mixed races, there is any transition from the Malay to the papuan type. I was soon satisfied by the first half-dozen I saw that they were of genuine papuan race, lighter in colour indeed than usual but still presenting the marked characters of the type in features & stature. They are scarcely darker than dark Malays & even lighter than many of the coast malays who have some mixture of papuan blood. Neither is their hair frizzly or woolly, but merely crisp or waved, yet it has a roughness or slight woolli¬ness, of appearance produced I think by the individual hairs not laying parallel & close together, which is very different from the smooth & glossy
though coarse tresses, everywhere found in the unmixed malayan race. Their stature alone marks them as distinct being decidedly above the average malay height, while the features are as palpably unmalay as those of the European or the negro.2
Wallace was convinced he had finally found the dividing line between the two ‘races’: a place where the Papuan and Malay species of man were totally separated without any evidence of a transitional form existing between the two. Wallace believed that this fitted his theory. If all other animal species were defined by the extinction of intermediate forms, why not man himself? He had always considered man to be a species of animal, and thus subject to natural laws. He had seen how precarious was the existence of some of the tribes, especially with regard to food supplies, when he had visited Aru. Some of the scenes he had witnessed while living for some weeks with two separate tribes of Papuans on the northernmost island of the Aru chain had made him think deeply about humans’ contin¬uous quest for food.
In his field journal, he noted that he had lived with a tribe of Papuans in their landlocked village of Wokan for two weeks at the end of March 1 857.3 He compared that tribe’s conditions of existence with those of another tribe of Papuans living in the coastal village of Wanumbai, with whom he lived for six weeks from the beginning of April.
Wallace made his feelings about man and beast clear from the outset. ‘The human inhabitants of these forests are not less interesting to me than the feathered tribes,’ he wrote in his journal, before addressing the condi¬tion of the Wokan villagers. ‘They are on the whole a miserable set of savages. They live much as all people in the lowest state of human exis¬tence live and it seems to me now a more miserable life than ever I have thought it before’.
Part of their dilemma, he recognised, was that they had no staple food, such as bread, rice or sago. Instead, their diet consisted of various vegeta¬bles, plantains, yams, sweet potatoes and crude sago. They also chewed ‘vast quantities’ of sugar cane, as well as betel, gambir and tobacco. He noted that sometimes their diet was supplemented by cockles and other shellfish, or sporadic feasts of wild pig and kangaroo. These were ‘too rarely to form anything like a regular part of their diet which is essentially vegetable, & what is of more importance as affecting their health, of green watery vegetables, roughly roasted or boiled & even this in varying & often insufficient quantities’.
Wallace thought the prevalence of skin disease and ulcers on the legs and joints of the villagers in Wokan were due to their inadequate diet. He
had seen the same kind of thing among tribal people elsewhere, caused by the ‘poorness and irregularity of their living’. Almost immediately, he realised that in the Amazon and now in the archipelago, tribes with staple diets were healthy and nourished, while those existing mostly on vegeta¬bles were in a poor condition.
[I] n this as in other respects man does not seem capable of making a beast of himself with impunity living from hand to mouth on the herbs and fruits of the earth alone. He must labour and select and prepare some farina¬ceous product capable of being stored to give him a regular daily staple food. When this is obtained he may add vegetables and fruits with advan¬tage, as well as animal food.
By contrast, in the village of Wanumbai, Wallace saw that the villagers
were far removed from the ‘miserable’ existence of the people of Wokan:4
They keep up a continual row from morning to night talking laughing shouting without intermission; not very pleasant but I take it as a study of national character and submit… All the men and boys are expert archers never stirring out without their bows and arrows. They shoot all kinds of birds as well as pigs and kangaroos occasionally, which give them a pretty regular supply of meat with their vegetables. The result of this better living is superior healthiness, well made bodies and generally clear skin.
It was this energy and determination that Wallace recognised as the major difference between the two villages. His account makes his conclusions obvious: ‘a people must exert diligence in procuring a steady food supply to maintain a state of healthiness.’
Wallace had also been disturbed by the way surface water disappeared through the ‘porous coralline rock’ of the island during any hint of a dry period. ‘Were there a dry season like that of Macassar,’ Wallace wrote, ‘Aru would be uninhabitable’.5 The inability of some tribes to organise for themselves the long-term provision of a staple foodstuff for their diet, and the vulnerability of the island-dwellers to anything like a long-term drought, dominated Wallace’s thoughts after his first visit to Aru.
Therefore, one year later, in February 1858, observing Papuan villagers from the east of Gilolo delivering sago and rice in abundance to villagers in the west, the plight of some of those Aru islanders could not have been far from his mind, especially as he was still attempting to find evidence of a transitional race between the Papuans and the Malays.6
We have no contemporary time-frame for what happened next. There
are no clues in Wallace’s field journal, nor any in the retrospective accounts. However, during the time he spent on Gilolo during that February, something happened to Wallace’s thinking that resulted in one of the most astonishing intellectual feats in the history of science.
Many years later, Wallace described how, while suffering from a ‘sharp attack of intermittent fever which obliged me to lie down every afternoon during the cold and subsequent hot fits which lasted together two or three hours’, the answer to the species question suddenly occurred to him.7
It was during one of these fits, while I was thinking over the possible mode of origin of new species, that somehow my thought turned to the ‘positive checks’ to increase among savages and others described in much detail in the celebrated Essay on Population by Malthus, a work I had read a dozen years before.
These checks – disease, famine, accidents, wars etc – are what keep down the population, and it suddenly occurred to me that in the case of wild animals these checks would act with much more severity, and as the lower order of animals all tended to increase more rapidly than man, while their population remained on the average constant, there suddenly flashed upon me the idea of the survival of the fittest – that these individ¬uals which every year are removed by these causes – termed collectively ‘the struggle for existence’ – must on the average and in the long run be inferior in some one or more ways to those which managed to survive.
The more I thought of this the more certain it appeared to be; while the only alternative theory – that those who succumbed to enemies, or want of food, or disease, drought or cold be every way and always as well constituted as those that survived – seemed to me impossible and unthink¬able.
Wallace wrote that account in 1903, when he was a year away from his eightieth birthday, but the crucial elements of all five versions he wrote down between 1898 and 1908 are the same. In 1905, he commented on what was meant by the process he had described:8
Then it suddenly flashed upon me that this self-acting process would necessarily improve the race, because in every generation the inferior would inevitably be killed off and the superior one would remain – that is, the fittest would survive. Then, at once, I seemed to see the whole effect of this, that when changes of land and sea, or of climate, or of food supply, or of enemies occurred – and we know that such changes have always been taking place and considering the amount of individual variation that my
experience as a collector has shown me to exist, then it followed that all the changes necessary for the adaptation of the species to the changing conditions would be brought about; and as great changes in the environ¬ment are always slow, there would be ample time for the change to be effected by the survival of the best fitted in every generation. In this way every part of an animal’s organisation could be modified exactly as required and in the very process of this modification the unmodified would die out, and thus the definite characters and the clear isolation of each new species would be explained.
Wallace was convinced he was right:
The more I thought it over the more I became convinced that I had at length found the long-sought-for law of nature that solved the problem of the origin of species. For the next hour I thought over the deficiencies in the theories of Lamarck and of the author of ‘Vestiges’ and I saw my new theory supplemented these views and obviated every important difficulty. I waited anxiously for the termination of my fit so that I might at once make notes for a paper on the subject. The same evening I did this pretty fully, and on the two succeeding evenings wrote it carefully in order to send it to Darwin by the next post which would leave in a day or two.
Wallace dated his paper ‘Ternate, February 1858’.9 It can be broken down into eight significant steps.10
1 Varieties can be expected to differ in organization and habits (and hence in their ability to gather food) from each other and from the ‘parent species’.
2 Even slight differences will make a variety ‘inferior’ or ‘superior’ to the parent species under a given set of conditions.
3 The size of any population is a reflection of its food-gathering ability, not of its reproductive capacities.
4 Suppose, then, that a ‘parent species’ is represented in different geographical areas by an ‘inferior’ and a ‘superior’ variety. If the general circumstances worsen, as in a prolonged drought that makes food scarce, the populations of all three will dwindle.
5 However, the variety that is inferior in its food-gathering abilities (and consequently has a smaller population) will be the first to dwindle to extinction, followed by the parent species. At this point, only the superior variety will survive.
6 If conditions improve, and food becomes abundant, the population of
the surviving variety will increase and extend its range, eventually attaining the size and range of the three former populations.
7 Thus the superior variety replaces the parent species, becoming what must be called a ‘new’ species, and in time becoming a ‘parent’, geograph¬ical representatives of which may become new varieties.
8 The repetition of the process results in progressive development and continued divergence from the original type.
Wallace’s paper was entitled ‘On the Tendency of Varieties to Depart Indefinitely from the Original Type’. It was nothing less than a perfect description of the process of evolution, completed in just over four thou¬sand words (See Appendix 4).
The Dutch mail steamer Ambon,11 with the letter on board, departed from Ternate on 9 March 1858, on the first leg of a journey to England and the home of the unsuspecting Charles Darwin.