The amount and type
of genetic material, along
with carbon dating
of the samples, reveal that between 50,000 and 25,000 years ago — before the
peak of the
last ice age — arctic vegetation consisted mainly
of forbs, the researchers report today in Nature.
At the
peak of the
last ice age, about 20,000 years ago,
with New York City and large parts
of Europe and Asia buried under thick sheets
of ice, Earth's orbit shifted.