Ambling along the cobblestone paths of a Hindu Kush village, it
is not uncommon to chance upon cattle that stand just a metre
tall at the shoulder, or sheep that barely measure up to the
height of man's knee. Inured to the hard winters of Pakistan's
Chitral district and the limited resources on the mountain
plateaus, livestock has adapted, along with shaggy coats and
sure-footedness, towards smaller specimens of the species.
Examples abound of animals adapting to privation. A species of
fox on the California Channel Islands is no larger than a house
cat; a species of pygmy mammoth evolved on the same islands,
shrinking in size to accommodate the habitat, although it is of
course long extinct. Environmental constraints are a hard fact
of life. And now it appears that the world as a whole is
becoming a more challenging habitat. A study published on Sunday
in the journal Nature Climate Change concluded in a survey of 85
plants and animals that there is a decades-long trend towards
smaller species, including ever