THE huge mastodons that roamed America at the end of the last ice age were
plagued by tuberculosis. The disease could have killed off the elephant-like
beasts or made them easier to hunt鈥攈elping to explain why they died
out.
鈥淭uberculosis was not simply endemic, but actually pandemic鈥�, a hyperdisease
that infected the entire population, says Bruce Rothschild, an arthritis
specialist who also studies fossil bones at the Carnegie Museum of Natural
History in Pittsburgh.
Rothschild鈥檚 suspicions were aroused when he spotted tuberculosis scars on a
museum specimen of a mastodon foot bone. The bacterium that causes tuberculosis
infects soft tissue, but can leave telltale scarring on the underlying bones.
When Rothschild examined the bones of a further 48 mastodons held in museum
collections, 21 of the animals had at least one bone with tuberculosis scarring,
he told a meeting of The Society of Vertebrate Paleontology in Bozeman, Montana.
Advertisement
Curiously, Rothschild found no tuberculosis scars on bones from
mammoths鈥攖aller relatives of the mastodons. Larry Martin, a
palaeontologist at the University of Kansas in Lawrence, reckons the mammoths
may not have been infected, as they tended to live in open, grassy environments.
The mastodons preferred wetter forests, where they may have been more likely to
catch the bug from the soil.
Even if tuberculosis did kill off the mastodons, the wave of extinctions that
swept across North America 13,000 years ago was still most probably due to human
hunters, says Paul Martin of the University of Arizona in Tucson. Around 30
genera of large animals disappeared about the same time.
However, Rothschild says some of the mastodon bones clearly predate the
arrival of humans, confirming that people did not bring the disease to the
Americas. And other work by Rothschild and Martin has cast doubt on the theory
that human tuberculosis evolved from the bovine form when cattle were first
domesticated. They recently isolated DNA from the human form of tuberculosis
from a 17,000-year-old bone of a North American bison. 鈥淭hat throws out the
whole domestication concept,鈥� Rothschild told New Scientist.