Tuesday, August 23, 2016

Earliest ancestor of living things

How and where life arose out of inanimate
matter is a mystery that has long
consumed evolutionary biologists.
Charles Darwin famously speculated
that the first living things arose in some
“warm little pond.” But a new genetic
study suggests life first formed in a far
less hospitable environment: scalding
deep-sea hydrothermal vents—gas-filled
plumes created by the interaction of
seawater and magma erupting through
the ocean floor. Biologists at Heinrich
Heine University in Germany arrived at
that conclusion after creating a detailed
genetic profile of a 4 billion–year-old
organism dubbed Luca, an acronym for
the Last Universal Common Ancestor.
The researchers examined 6.1 million
protein-coding genes found in bacteria
and archaea—single-celled organisms
with no nucleus (prokaryotes) that eventually
gave rise to all plants and animals
(eukaryotes), The New York Times reports.
After arranging the genes in evolutionary
family trees, they found that 355
likely originated from Luca. The genetic
reconstruction suggests Luca thrived in
an intensely hot setting devoid of oxygen
and relied on hydrogen and metals
for energy, precisely the conditions in
deep-sea vents. “I was flabbergasted at
the result—I couldn’t believe it,” says
study leader William Martin. His research
doesn’t confirm that life began in the
vents: Some biologists believe the first
organisms started out on land, but may
have been propelled undersea 4 billion
years ago, after a shower of asteroids
and comets reshaped the planet.


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