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Land Plants Origins Pushed Back
Not dinos but still rather interesting.
When the first pioneering plants emerged from the earth's
ancient seas and took up life on land, they turned a barren
landscape green and paved the way for countless
animals and other organisms to follow.
Biologists have long set the date for that momentous event
somewhere around 450 million years ago, but a new study in
the current issue of the journal Science suggests that
plants escaped the oceans at least 700 million years ago,
a radically earlier date.
In fact, the new work pushes the origin of land plants so
far back in time that the authors say these plants may
actually have touched off critical events that have long
been thought to have predated them. One such event is the
famous evolutionary proliferation of animal groups called
the Cambrian explosion.
Published on Friday, the new date of 700 million years has
already garnered great interest as well as healthy portions
of head-shaking disbelief. The team of researchers, composed
largely of undergraduates at Penn State, was led by Dr. Blair
Hedges, a molecular evolutionist known for using molecular
data to try to turn conventional wisdom about evolutionary
history on its head.
The work is also of interest as the latest in what is
becoming a long line of molecular studies that suggest ages
that are inexplicably older than fossil data would suggest
for various groups. Some scientists say that the molecular
data are likely to be right and that paleontologists need to
dig harder for those fossils. Others suggest that molecular
data may be biased toward overestimating ages.
In their study, Dr. Hedges and colleagues analyzed more
than 100 previously published protein sequences to examine
the differences accumulated over time between a number of
fungi and plants.
Plants are widely thought to have made the leap to land
accompanied by fungi, like the fungi that today can be
found living in the roots of most plants. Using a protein
clock, the researchers estimated that the necessary fungi
were around more than a billion years ago, setting the
scene for the evolution of land plants arising at least
700 million years ago.
Dr. Blair said the work suggested that biologists might
need to rethink the dating of some of the more modern
groups of plants, like the flowering plants and species
like corn and rice. "It could push these dates back also,"
he said, "and that probably will tick off a lot of people."