Chapter The Tree of Life and Death of The Origin of Species - Study Guide by Charles Darwin

The Tree of Life and Death

Many school textbooks still contain the archetypal illustration of a line of apes and ape-men proceeding from a slumped simian through specimens of stooping hominids to upright bowler-hatted modern man - marching inevitably and progressively towards biological modernity. Not only does such an illustration imply a teleological drive towards humanity (a crime enough in itself), but it fundamentally ignores the basic pattern of evolution and speciation. Survival of the best fitted necessarily requires the non-survival of the unfitted, not only in terms of individuals but eventually in terms of populations and species. We are all familiar with mass- extinction events such as the demise of the dinosaurs, and the loss of species wrought by man's ecological terrorism, but extinction is an inevitable and necessary natural process: "... as from the high geometrical ration of increase of all organic beings, each area is already fully stocked with inhabitants, it follows that as each selected and favoured form increase in number, so will the less favoured forms decrease and become rare. Rarity, as geology tells us, is the precursor to extinction… rare species will be… beaten in the race for life by the modified descendents of the commoner species." In other words we are left with a constantly budding and diverging bush of life, sporadically pruned by the shears of extinction. Whilst one of those stooping primates may have been our direct ancestor, others were evolutionary cul-de-sacs, or distant cousin-branches still growing. Homo sapiens did not, as is sometimes construed, evolve from, for example, Neanderthals. Rather, Homo sapiens replaced them to their cost. The branch of Neanderthal withered, whilst Homo sapiens prospered. The overall picture is that, "As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever branching and beautiful ramifications." Like those dauntingly complex Victorian family trees, "The natural system is a genealogical arrangement."