After the Sarawak Law: Evolutionary Biology in Borneo since 1855
Schilthuizen, Menno, Borneo Research Bulletin
In February 1855, while taking a rainy season break from his insect collecting at Rajah James Brooke's bungalow in Santubong, English naturalist Alfred Russel Wallace penned a short paper entitled "On the Law Which Has Regulated the Introduction of New Species." He sent the paper to the Annals and Magazine of Natural History, which published it in September of that same year.
In the ten-page article, Wallace elaborated on the phenomenon that related species are always found in close geographical proximity to each other and that species known as fossils usually have their closest relatives in the same geological layer. Drawing the logical conclusion, he proposed the biological law that "Every species has come into existence coincident both in space and time with a pre-existing closely allied species" (Wallace 1855).
The meaning of this "Sarawak Law," as is has become known, is that a new species appears either by the transmutation of an ancestral species, or by splitting off from an ancestral species (without the latter disappearing). Such a sequence of events clearly is supportive of evolution, not of divine creation. Therefore, the paper is generally considered as one of the key steps towards Darwin and Wallace's joint discovery and publication of the mechanism of evolution by natural selection, three years later (Slotten, 2004).
Yet, it would be a misunderstanding to think that his field work in Borneo was what convinced Wallace of the reality of evolution. The 1855 paper draws on a diversity of evidence, but most of it comes from the literature and from Wallace's travels in the Amazon and in Britain--it could have been written anywhere. Nevertheless, by writing his paper in Sarawak, Wallace firmly placed the cradle of evolutionary biology in Borneo. Moreover, his vast zoological collections from the island have been one of the bases upon which further taxonomic and evolutionary work in Borneo has been founded. Consequently, it is of more than passing interest to investigate how evolutionary studies have progressed in Borneo in the one and a half centuries since.
In this paper, I review the main events in Bornean evolutionary biology over the past 150 years. By necessity, this includes mostly research carried out by overseas researchers. Only very recently have evolutionary studies been based in universities and other research institutions on the island itself. I also make comparisons with the situation in parts of the world that are geographically comparable to Borneo. I conclude that, in spite of its auspicious beginnings and a number of beneficial factors, Borneo has played a relatively minor role in the development of evolutionary biology. However, if a shift in research policies were to take place, this situation could soon change for the better.
Background: Evolutionary Biology Worldwide 1855-2005
To place the developments in Bornean evolutionary biology in perspective, let me begin by sketching the main events in this field on a global scale. Darwin and Wallace (1858) and Darwin (1859, 1871) published the outlines of evolution by natural and sexual selection, which have survived essentially unchanged till the present time. However, a comprehensive research program only began to develop in the 1930s, after the broad acceptance of Mendelian genetics (Dobzhansy 1937), the mathematical development of population genetics (Fisher 1930), and the thinking of evolution in terms of populations (Mayr 1942). Later, this body of insights (collectively known as Neodarwinism) was complemented with the logical framework for reconstructing evolutionary trees (Hennig 1950). Before the 1930s, very few studies were undertaken with a distinct evolutionary focus. However, data were amassed in systematics and biogeography that have formed the foundation for later, evolutionary work. Among the major developments in evolutionary biology in the neodarwinian era, I would like to highlight the following:
(1) Phylogenetics. …