I found this very interesting piece on the 19th century biologist, Karl Wilhelm Nageli, and August Weismann in Richard L. Gregory’s Mind In Science (London: Penguin 1981). The modern theory of evolution, NeoDarwinism, is essentially a mixture of Darwin’s theory of evolution by natural selection mixed with Mendelian genetics. Roughly speaking, it views evolution as proceeding through random mutations. These supply the variations in species on which natural selection works, weeding out those varieties that don’t help the species to survive. Those that do, or at least don’t stop it surviving, are preserved and retained. Thus the little alterations in the characteristics of different species are created, which gradually accumulate over millennia and millions of years to produce new species of creature.
Darwin, however, didn’t know about heredity, which was introduced into his evolutionary theory by Weismann. He had developed the germ plasm theory, which was the precursor to the modern theory of DNA, famously discovered by Crick and Watson. Darwin also didn’t know about mutations either. He believed that heredity was a blending of the characteristics of the parents. I’ve got a feeling this was one of the arguments his opponents may have used against his theory, and that Darwin probably recognized the weakness of his theory there. At the time Darwin proposed his theory of evolution, I don’t think he was properly able to account for the emergence of novel characteristics in living creatures, on which natural selection acted.
It was Karl Wilhelm Nageli, who did this by introducing mutations into evolutionary theory, while rejecting Darwin’s idea of Natural Selection. Unlike evolutionary biologists after him, however, Nageli believed that these mutations had a purpose. It was the Dutch biologist Hugo de Vries, who introduced Mendelian genetics and the variation of characteristics into Darwinian evolutionary theory. Gregory explains it thus:
Neo-Darwinism adds to Darwinian Natural Selection a theory of heredity, which is itself derived from the, at the time (and perhaps still), controversial writings of the German biologist August Weismann (1834-1914). His papers (1868-76), translated into English as Studies in the Theory of Descent, (1882) proposed properties of a germ plasm which are similar to the fundamental doctrine of molecular biology, that information can only genetically pass from coded DNA to messenger RNA, and not the other way round. This genetic ‘diode’ rejects Lamarckian inheritance of individually acquired knowledge, or adaptive behavior. But we jump ahead, for Darwin had no knowledge of genes or mutations of genes.
The concept of evolution by mutational jumps is due to a Swiss botanist, Karl Wilhelm Nageli (1817). Nageli however rejected Darwin’s theory, for he supposed that there is a purpose in the direction of the jumps. He is heavily criticized for failing to appreciate the significance of Mendel’s work. He was shown the manuscript of Mendel’s paper describing his experiments on the breeding of giant and dwarf peas; his lack of interest is supposed to have prevented the work becoming known so that genetics was held up by some fifty years. Nageli’s concept of mutational jumps, but without built-in directional purpose, was developed by De Vries early in the present century.
Gregor Johan Mendel (1822-84) was an Augustinian monk. At the Abbey of St Thomas in Brunn, [Brno] he carried out his plant-breeding experiments, which depended on counting the proportions of tall and dwarf peas obtained by self-pollination. He found that the varieties did not converge to a medium-height pea plant, but that the tall and dwarf characteristics were maintained, and potentially present, in each variety. This was immensely important for Darwin’s theory, but unfortunately Darwin never came to hear of it.
The mutation theory was developed by the Dutch botanist Hugo De Vreis (1848-1935) who approached Mendel’s discovery by seeing that something like it was needed to give the variataion necessary for Natural Selection. He proposed that different characteristics might vary independently, and recombine in different ways. So was born the atomic-characteristic theory of inheritance, which later was embodied in gene and chromosome code structures – from which in turn developed modern molecular biology with the discovery by Francis Crick (b. 1916) and James Watson (b. 1928) of the structure of the long helical molecules of deoxyribonucleic acid (DNA). This, by replication, gives the physical basis of inheritance. Random change of the DNA structure give the variation necessary for Natural Selection. The drama of this discovery is superbly presented by Watson in The Double Helix (1968). (pp. 170-1).
Back in the 1980s, the astronomers Fred Hoyle and Chandra Wickramasinghe attacked Darwinian evolutionary theory in their book, Evolution from Space. In their previous book, Life Cloud, they had argued that life on Earth was seeded on Earth from space. While it’s an unorthodox theory, many scientists do believe that such panspermia, as it’s called, is a possibility. And the amino acids which form the basic building blocks of organic life has been found in meteorites, on Saturn’s moon, Titan, and in the nebulae, the clouds of dust and gas in space. What is far more controversial, and has been rejected by nearly all scientists, is their theory in Evolution from Space that the chance of organic life arising on Earth, and developing through Darwinian evolution, is so minute that evolution has to be directed by alien civilisations seeding space with the necessary genetic material.
In one passage in Evolution from Space, Hoyle and Wickramasinghe take the incidence of mutations in every generation, only a minority of which could be beneficial, and the combined length of time from the split, early in our evolutionary history, between the hominid lineage and the common ancestor of chimpanzees and gorillas 9 million years to argue that even this amount of time is insufficient to produce modern Homo Sapiens Sapiens, modern humanity. I’ve no doubt that this was immensely controversial and has been widely criticized and dismissed. It’s been taken up again more recently by the Intelligent Design people. And it wasn’t the weirdest of Hoyle’s and Wickramasinghe’s ideas. I think they also believed that the civilisations seeding this genetic material were computers in parallel universes. But if they are right after all, and random mutation can’t account for the development of the vast variety of living creatures we see around us, then it may be that it proceeds through purposeful mutations after all.
Going back to Nageli, even if his own theory of evolution has been discarded except for the idea of mutational jumps, I would far, far rather believe that evolution and the mutations necessary for it were shaped and guided by a loving creator, than are simply the result of blind chance as describes by Richard Dawkins in his book, The Blind Watchmaker.
Beastrabban\'s Weblog 