Published in 1859, Charles Darwin's On the Origin of Species made a number of brave claims about the nature of evolution — including the suggestion that an animal species with greater diversity in its line will produce more subspecies too. This assumption is not as obvious as you might think at first. And it was finally found to be true for birds only a couple of years ago. Now, researchers from the University of Cambridge in the UK have shown that Darwin was right on this point for mammals (哺乳动物), too.
Apart from being an important contribution to our understanding of evolution in general, the findings could also be useful in ongoing conservation efforts — helping experts to figure out which species need to be protected in order to ensure their survival.
"My research investigating the relationship between species and the variety of subspecies proves that subspecies play a vital role in long-term evolutionary dynamics and in future evolution of species," says biological anthropologist Laura van Holstein. There are three subspecies of northern giraffe, for example, and 45 subspecies of the red fox — the highest in the animal kingdom. 36 different species of wild cats have been found and most of these are further divided into subspecies. Human beings, on the other hand, don't have any subspecies.
To test Darwin's assumption, van Holstein looked at a huge database of animal classifications, analysing the collected knowledge we have about mammal species and subspecies to look for patterns. The data showed that habitat (land versus sea, for example) plays an important role in subspecies' form and increase. The findings show that those living in the sea, or spending a lot of time in the air are less affected by physical boundaries like mountains.
The discoveries on subspecies habitat are particularly significant when it comes to conservation, because the habitats of so many animals are under threat from climate change and human activity, and these findings indicate that our actions really are having an effect on the process of evolution.
