Read more: 鈥�Unnatural selection: How humans are driving evolution鈥�
Most predators target the young or the weak. We are different, targeting the biggest and best, or those with characteristics we desire, such as large antlers. Combine this with our ability to kill in great number and the result is extremely rapid evolution of our prey.
The first clear evidence was published in 1942, and since then many examples have emerged of how hunting can transform the hunted. The targeting of large animals has resulted in a fall in the average size of caribou in some areas, for instance, while trophy hunting has led to bighorn sheep in Canada and mouflon in France evolving smaller horns.
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Perhaps the most dramatic example is the shrinking of tusks in elephants, or even their complete loss. In eastern Zambia, the proportion of tuskless female elephants shot up from 10 per cent in 1969 to nearly 40 per cent in 1989 as a result of poaching (). Less dramatic rises in tusklessness have been reported in many other parts of Africa, with some bull elephants losing tusks too.
Humans have had an even bigger impact in Asia. Only male Asian elephants have tusks, and the proportion of tuskless bulls has soared in many areas. In Sri Lanka, where there has been a lot of poaching, under 5 per cent of males now have tusks, says of the Indian Institute of Science in Bangalore, who studies Asian elephants. Simulations by of the University of Potsdam in Germany and colleagues suggest that female elephants鈥� preference for tuskers has partly counteracted the effect of hunting. However, even if all poaching stopped, it would take a very long time for the percentage of tuskers to rise again.
It鈥檚 not just animals that are being shaped by human preferences: the harvesting of wild plants can have a similar effect to hunting and fishing. In Tibet, for example, the height of the snow lotus at flowering has nearly halved over the past century as a result of the flowers being picked for use in traditional medicine ().
To even the balance, some biologists are now promoting the idea of counteracting the evolutionary pressures of hunting through 鈥渃ompensatory culling鈥� 鈥� killing animals with undesirable traits. This has actually long been done in some places. In Germany and Poland, for instance, there is a tradition of shooting yearling deer with poor antlers to prevent a decrease in the antler size of mature stags.
Private reserves in countries such as Zimbabwe have a similar policy. They typically charge hunters a smaller 鈥渢rophy fee鈥� for shooting tuskless elephants 鈥� $3000 versus at least $12,500 for a tusker, for example. This is partly because tuskless animals are less valuable, but it is also a deliberate attempt to eliminate the trait.
Read next article: 鈥�Unnatural selection: The race against climate change鈥�
