Study traces humanity's origins
2013-02-08 20:48
-
Us
An old fashioned story by Mary Louisa Molesworth (1836-1921). The author of beloved children's...
Now R150.00
buy now
Washington - Humans may have descended from apes, but
long before that there was a small, four-legged insect-eating critter,
according to new research out on Thursday in the US journal Science.
The international six-year study used a massive trove of
data, including genetic and physical traits from both modern and prehistoric
species, to reconstruct the extended family tree of mammals.
The researchers focused on the "placental
mammals" a branch of species that includes humans, horses, whales and many
others.
The project has helped scientists better understand how
and when modern placental mammals evolved, and, importantly, has traced the
starting point to after dinosaurs went extinct 65 million years ago.
The researchers say the new information will help them
study a vital question facing the world today: How mammals may have survived
past instances of climate change and how that might help us face the warming
now underway.
"Species like rodents and primates did not share the
Earth with non-avian dinosaurs but arose from a common ancestor - a small,
insect-eating, scampering animal - shortly after the dinosaurs' demise,"
said lead author Maureen O'Leary of New York's Stony Brook University.
The new conclusion overturns an earlier, commonly-held
hypothesis that there was a diverse crew of placental mammals before the event
that led to the disappearance of dinosaurs and 70% of the planet's species.
That theory had been based exclusively on genetic data.
But scientists said combining the genetic evidence with anatomical and fossil
evidence helped create a clearer picture of the history.
"Discovering the tree of life is like piecing
together a crime scene - it is a story that happened in the past that you can't
repeat," Leary said.
"Just like with a crime scene, the new tools of DNA
add important information, but so do other physical clues like a body or, in
the scientific realm, fossils and anatomy. Combining all the evidence produces
the most informed reconstruction of a past event."
According to the new theory, some 200 000 to 400 000
years after dinosaurs went extinct, the little placental mammal started
evolving along a number of different paths, giving rise to the incredible
diversity of species we've seen in the eons since - including more than 5 100
living today.
The study also helped illuminate the evolutionary history
that led from this common ancestor through to modern-day animals, and showed,
for instance, that one group of African animals, including elephants and
aardvarks, first developed in the Americas.
"Determining how these animals first made it to
Africa is now an important research question along with many others that can be
addressed using MorphoBank and the phylophenomic tree produced in this
study," said author Fernando Perini, of Brazil's Minas Gerais Federal
University.
Mary Silcox, of the University of Toronto Scarborough,
added "this project is not exhaustive, but exposes a way forward to
collect data on other phenomic systems and other species."
