|
|
|
|
|
|
|
|
SCIENCE:
Evolution Faster
Than We Thought
Francesca
Colombo*
BERN, Switzerland,
(Tierramérica) - Husband-wife
science team Peter and Rosemary
Grant, both 69 years old, have
been following the footsteps of
Charles Darwin in the Galapagos
Islands since 1973. Through
meticulous measurements of the
beaks of finches and studying
their song over several decades,
they were able to document the
speed of the natural selection
process.
Their study focussed on 25
generations of these small birds
-- some 19,000 in total --
belonging to 14 finch species on
Daphne Island in the
archipelago, located 1,000 km
from the coast of Ecuador in the
Pacific Ocean.
"We proved three things: the
first is that the process of
natural selection is faster than
Darwin thought. We discovered
the number of genetic variations
in the shape of the beak and the
body in the natural populations"
of finches, British-born Peter
Grant told Tierramérica.
"Second, we documented the
mechanism through which
different populations of finches
can be isolated in reproduction
and become new species; and
third, that the 14 species in
the Galapagos evolved from a
common branch of birds that
arrived on the islands two or
three million years ago,"
summarised Grant.
For their life work, on Nov. 11
in the Swiss city of Bern, the
Grants received the 2005 Balzan
Prize for population biology,
recognising their scientific
excellence and contribution to
the world of science.
"The two scientists explained
the mechanisms through which new
species emerge and how genetic
diversity is maintained in
natural populations. The work of
the Grants is the most
significant study of evolution
in recent decades," says the
International Balzan Foundation,
which awards the prize.
Rosemary and Peter are both
biologists and professors at
Princeton University in the
United States, author of several
books, and the subject of
another, "The Beak of the Finch:
A Story of Evolution in Our
Times", written by Jonathan
Weiner, winner of the 1994
Pulitzer Prize.
The investigations of the
Grants, who are also founders of
the Charles Darwin Research
Station in the Galapagos,
demonstrated that the rapid
mutations in the sizes of the
body and the beak of the finches
in response to availability of
food are guided by natural
selection.
The concept of natural selection
-- part of Darwin's theory of
evolution -- maintains that
environmental conditions
determine the effectiveness of
certain traits in living
organisms for their survival and
reproduction.
The Grants observed, for
example, that in years of
drought, like 1977, when there
were reduced supplies of seeds
for the finches to feed on,
natural selection favoured those
with larger and deeper beaks.
Many of the smaller finches did
not survive.
But this situation changed with
the torrential rains that
accompanied the climate
phenomenon known as El Niño in
1982. The rainfall left small
seeds that were the staple of
small finches, better suited
than their "cousins" with larger
beaks. They adapted and
reproduced.
"Our investigation studied the
process of these adaptations,
and we established that these
changes occurred in a few years,
and are steps towards producing
new species of birds," Rosemary
Grant, born in Scotland, said in
a Tierramérica interview in Bern
when she and her husband
received the Balzan Prize.
The scientists not only pursued
the work started by Darwin
(1809-1882) but also confirmed
his hypothesis.
Aboard the HMS Beagle, Darwin
visited the Galapagos in 1835,
and from his studies there,
deduced that the diverse species
of finches with different beaks
were the result of local
ecological conditions and
natural selection. These
theories about how new species
formed turned into the basis of
his celebrated work "The Origin
of Species", published in 1859.
The biologists studied the 14
Darwin finch species, which
include small tree finches (Camarhynchus
parvulus), sharp-beaked finches
(Geospiza nebulosa), vegetarian
tree finches (Platyspiza
crassirostris), and cactus
finches (Geospiza scandens),
among others.
For the scientists, the
Galapagos finches (black males,
brown females), who nest in
trees and eat insects, or on the
ground and eat seeds and
flowers, were the perfect object
of study, due to the simplicity
of their undisturbed habitat.
"The changes in the environment
and the influence of the
currents of El Niño and La Niña
create a very special situation.
The finches are trapped by these
conditions and their changes
occur more quickly," said Peter
Grant.
The Grants also identified gene
Bmp4, which influences the
development of beak shape, in
addition to proving that these
species descend from a common
branch of finches that reached
the Galapagos two or three
million years ago.
This gene could play an
important role in how these
small birds evolved and continue
to evolve.
Although they live in the United
States, the Grants return to the
islands regularly, and plan to
continue their research there in
January. Their daughter Thalia,
also a biologist and scientific
illustrator, lives in the
Galapagos.
(* Francesca Colombo is a
Tierramérica contributor.
Originally published Nov. 19 by
Latin American newspapers that
are part of the Tierramérica
network. Tierramérica is a
specialised news service
produced by IPS with the
backingof the United Nations
Development Programme and the
United Nations Environment
Programme.) |
|
|
|
|
|
|
