Travel Reference
In-Depth Information
animal species and almost 300,000 plant species. Do all these named species
have any objective existence, or are they simply artifacts of our tendency to
compartmentalize the world in order to make sense of it? Is there really a dif-
ference between the golden and the woolly lemur, and if so what is it? And
does the dif erence matter?
In this chapter we will see that species are real, and that they are an inevi-
table product of the interaction between the gene pools of populations and
the evolutionary forces that act on them. And we will see that the total num-
ber of species that can live in a given environment depends on how complex,
energy-rich, and stable that environment is.
How lemurs have become many species
In Chapter 3 we saw how India split of from Africa over 200 million years
ago and began to move rapidly (at least in tectonic terms) northward toward
the continent of Asia. Ninety million years ago the island of Madagascar split
of from India in turn, and was left behind as India headed for an immense
collision with the world's most massive tectonic plate. This vast collision
would produce the Himalayas.
After Madagascar split of from India it was marooned in the middle of
the Indian Ocean. It initially carried a freight of animals and plants that had
originated while Gondwana was still an intact continent. But many of its fi rst
inhabitants were lost to extinction, and many of the ancestors of the pres-
ent-day animals and plants of Madagascar were carried to the island more
recently from Africa.
All the forty-nine lemur species today, and an unknown number of lemur
species that have gone extinct, are descended from a tiny group of ancestral
primates that somehow made their way to the island from Africa about 60
million years ago. They probably clung to trees that had been washed out to
sea by a giant storm and then blown to a lonely Madagascar beach—rather
like the animal escapees from the Central Park Zoo that made a more recent
landfall on the island in the hopelessly inaccurate (but decidedly funny) ani-
mated movie
Madagascar
.
