Download Diane Thajeb Darwin`s Finches and how his study of them led to the

Diane Thajeb
Darwin’s Finches and how his study of them led to the Theory of Natural Selection
Everyone knows who Charles Darwin is. He is the person who everyone credited the theory
of natural selection with. But how did he exactly stumble on the Natural Selection? Did he
just sit there and think, and there it was? He was just a normal young man who discovered
his love for biology in 1828 when his father sent him to Cambridge university to study
theology. He met the geologist Adam Sedgewick and the naturalist John Henslow, who
helped trigger his love for biology.
At this time he also rejected the Theory of Natural Selection. After he graduated from
Cambridge University, his mentor Henslow helped secured him a job on a British Navy
mapping expedition that was to go around the world on the H.M.S Beagle and would last for
five years. The five-week stay at the Galápagos Islands, where he studied of the finches,
would lead him to produce several theories that eventually build up to the theory of Natural
Selection.
In September 1835, Darwin came to the Galápagos Islands to study the native species there.
During his visit to the Galápagos Islands, it occurred to him that the finches slightly varied
between each island. They were not huge differences; the differences he noticed was that
the size and shape of their beaks, and how they were colored. He then connected the reason
of these variations to the environment. The finches of the Galápagos Islands were similar to
the finches of the mainland of South America. In fact, they were thought to have originally
come from there. But although the species were alike, he knew that these finches were
special in the Galápagos Islands and would not be found anywhere else. He noticed the
finches of the Galápagos Islands had a variation from each other in beak size and shape. He
realized that the beak differences had to do with the food they would normally eat. Their
beaks were specialized to make it easier for them to find their food. For example, a finch
that eats fruits or buds tends to have a larger beak then one that eats insects, who tends to
have a sharper and thinner beak. Each variation of the beaks had their usefulness, some
were better at cracking nuts, others for catching insects, and so on. Darwin stumbled upon
adaptive radiation, well, now it’s called that. How he did that was he reached to the
conclusion that the original South American finches who had reached the islands had
dispersed to different environments where they adapted to the environment. Over many
generations of living on the Galápagos Islands their biology changed a bit to adapt to their
surrounding environment. He came to the conclusion that the thirteen species of finches he
found on the Islands had evolved from one ancestral species that was most likely originally
from the mainland. Each of the thirteen filled a different niche. A niche is the role of the
species, as in the resources it consumes and the habitat it lives in. Adaptive radiation, as
quoted from pbs.org, means “The diversification, over evolutionary time, of a species or group of
species into several different species or subspecies that are typically adapted to different ecological
niches.”
Darwin deduced that the finches had either evolved or adapted the Galápagos Islands after their
ancestors from the mainland were blown off course into the Islands. He came to
understand that within a population there are individuals that are all slightly different from
each other, the ones who have the differences that helped them survive better tend to get
more of their genes passed down and those who do not have advantageous differences
tend to not have as much of their genes pass down to the newer generations. They tend die
out in fact. It is fairly obvious why though. Those who can get more food and live better will
naturally be in better condition to mate then those who can’t find food in their
surroundings would probably die from starvation or are in worse conditions to mate .The
ones with the advantageous traits will eventually become common within the species as
more of their genes gets passed down and Darwin called this “descent with modification.” This
is called the Theory of Natural Selection.
In the end, even though he just studied the finches on the Islands, it played an essential role
in formulating the theory of Natural Selection. He was able to observe the differences between the
thirteen types of finches and connect it to the finches from the mainland of South America. He
managed to make the conclusion that the finches from the mainland were their ancestors and that
when they were blown off course. The finches eventually separated into thirteen categories as
natural selection took away the finches that could not survive on the islands and chose the ones
that have beaks to survive and were well equipped to get the type of food according to the category
of the finch. Through these observations, he formulated one of the main idea points to evolution
itself.
Bibliography
• “Darwin's Finches, Decent with Modification and Natural Selection”,
http://www.fossilmuseum.net/Evolution/DarwinsFinches.htm
• “Darwin’s Finches and Natural Selection”,
http://www.biology-online.org/2/11_natural_selection.htm
• Martyn Shuttleworth, “Darwin’s Finches”,
http://www.experiment-resources.com/darwins-finches.html

“Glossary”
http://www.pbs.org/wgbh/evolution/library/glossary/glossary.html#niche

“Darwin’s Finches- How Natural Selection was discovered”
http://www.experiment-resources.com/darwins-finches.html

“Early theories of Evolution: Darwin and Natural Selection”
http://anthro.palomar.edu/evolve/evolve_2.htm