Tuesday, June 16, 2009
Charles Darwin wrote about it 150 years ago: animals don't pick
their mates by pure chance – it's a process that is deliberate and
involves numerous factors. After decades of examining his work,
experts agree that he pretty much scored a scientific bullseye, but
a very big question is, "What have we learned since then?" asks a
Texas A&M University biologist who has studied Darwin's
theories.
Adam Jones, an evolutional biologist who has studied Darwin's work
for years, says that Darwin's beliefs about the choice of mates and
sexual selection being beyond mere chance have been proven correct,
as stated in Darwin's landmark book The Descent of Man, and
Selection in Relation to Sex. His work has withstood decades of
analysis and scrutiny, as Jones states in his paper, "Mate Choice
and Sexual Selection: What Have We Learned Since Darwin?" in the
current Proceedings of the National Academy of Sciences.
Bottom line: It's no accident that certain peahens submit to
gloriously-colored male peacocks, that lions get the females of
their choice or that humans spend hours primping to catch the
perfect spouses – it's a condition that is ingrained into all
creatures and a conscious "choice" is made between the two so the
romantic fireworks can begin.
Jones says Darwin set the standard for original thinking about
animal reproduction and was first scientist to propose plausible
mechanisms of evolution, and from there he took it one step further
– he confirmed that animals' mating choices can drive evolutionary
change.
"He noticed that birds, especially, seemed to be a bit picky about
who they mated with," Jones explains. "He discovered that birds –
especially females – had preferences and that they did not just
choose a mate randomly. He believed this is due to beauty of the
plumage, that females usually selected the most colorful
males.
"That was an important first step, and it's given us models to work
from to try to answer other big questions."
Those include determining methods to find out the actual criteria
used in choosing a mate, what methods work and which do not, and
the passing of genes on to the next generation, a field of study
Jones says gained popularity in the 1970s and 1980s.
"Another big recent advance was the development of molecular
markers, which allow us to perform paternity testing," Jones
adds.
"These markers can be applied to animal populations, and they give
us a definitive record of who is mating with whom and what
offspring resulted from the mating events. And also, what is the
driving force behind sexual selection? We have an unprecedented
ability to document mating patterns but we still don't completely
understand why some populations experience strong sexual selection
and others don't."
Jones notes that other key questions Darwin's work uncovered but
has not yet answered include the role of population characteristics
and the environment and how they work together to produce strong
sexual selection, and also what determines whether or not female
choice will evolve in a particular species.
And perhaps the biggest question of all: How does all of this
pertain to humans?
"Darwin concluded that sexual selection existed in the animal world
and that humans definitely followed a similar process," Jones
confirms.
"But he realized he had to explain it first as it related to
animals. Darwin thought that sexual selection was an important
process in humans, both for males and females. But how much has
sexual selection acted on males versus females in humans? Today,
while we are celebrating the 200th year of the birth of Charles
Darwin, we know sexual selection occurs and is very important but
there are still many unanswered questions about precisely why and
how it works, especially in humans."
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Texas A&M University
Thanks to Texas A&M University for this article.