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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."