Darwin's finches: clues to the origin of species

[Music] thank you [Music] thank you [Music] this is a paleontologist a scientist who studies and reconstructs the life of the past paleontologists tell us that living things have changed greatly since life first appeared on Earth they tell us that many kinds of animals have disappeared but they also say that many new kinds or species have come into being how do new kinds of living things come into being how do new species originate about 100 years ago Charles Darwin a young English scientist tried to answer these questions in the year 1832 Darwin was appointed Chief naturalist aboard a research ship the Beagle which was to sail around the world one purpose of this Voyage to collect plants and animals in many different places on this trip a tiny group of islands 500 miles west of the South American Coast proved most important for Darwin's observations the Galapagos Islands volcanic in origin these islands have never been connected with the mainland nevertheless despite their isolation they team with life on the Galapagos Darwin observed many familiar animals Penguins similar to those of the South polar regions swarms of crabs of many different kinds large but harmless land lizards called iguanas and small seed eating birds called finches Darwin reason that all these animals must have come from the mainland of South America but here on the Galapagos he saw other animals found nowhere else in the world gigantic tortoises that weighed over 500 pounds iguanas that swam in the ocean and long beaked finches that ate insects instead of seeds how did these new kinds of animals originate since they are found nowhere else they must have come into being here on the Galapagos Darwin studied the finches on these islands to explain their great variety he reasoned this way because of their geographic isolation the Galapagos Islands originally had no birds then many thousands of years ago a few finches with strong short seed cracking beaks must have flown there from the mainland in the absence of enemies seed eating finches multiplied and soon crowded the islands the increase in finches may have made seeds more difficult to obtain but as new finches were born slight differences or variations occurred among them perhaps one was born with a longer sharper beak this turned out to be a useful variation a long beak would enable it to pick up insects of all kinds insects were plentiful on the islands so this new Finch lived to pass on its longer sharper beak to some of its offspring and they in turn to theirs because their variation long beaks was useful for obtaining food these long beaked finches survived and reproduced alongside the Original Seed eaters after thousands of years long beaked finches came to form a new separate species of insect eating Finch the process by which useful variations result in new species Darwin called natural selection on these same Islands we can see variation and natural selection at work by observing another group of animals the iguanas these land iguanas like those on the mainland are sturdy animals with long round tails but here and only here on the Galapagos Darwin found another kind of iguana and ocean living or marine iguana with webbed feet and a flat tail the marine iguanas are similar to land iguanas but their webbed feet and their flattened Tails enable them to swim well and so suit them to water life they live along the rocky Shore at low tide they crawl among the rocks foraging for exposed seaweed how did these new marine iguanas come into being did they evolve from the land iguanas Darwin reasoned in this way the original Galapagos iguanas were land iguanas lacking natural enemies they had multiplied rapidly increased population may have made food scarce but not all the iguanas were exactly alike as new ones were born variations occurred among them perhaps some were born with flattened Tails or slightly webbed feet this was a useful variation because flat tails and webbed feet enabled these iguanas to swim in the ocean and their new surroundings offered them a new source of food they survived and multiplied to pass on their useful variation to their descendants through variation and natural selection a new species of iguana a marine iguana originated for almost 30 years Darwin gathered evidence to support his theory then in 1859 he published a book called The Origin of Species presenting his ideas on the way in which different kinds of living things come into being he said there is a struggle for existence because many more individuals are born than can possibly survive he said there is variation because no two individuals even of the same kind are exactly alike he said there will be natural selection as individuals pass on their useful variations to their offspring generation succeeds generation and new kinds of animals gradually make their appearance thus new species originate in this way said Darwin the vast variety of living things have all originated through variation and natural selection one kind evolves from another all are different yet all are related almost a century and a half have passed since Darwin's voyage to the Galapagos by studying many kinds of living things we have learned much about the Origin of Species but few animals have had more effect on scientific thinking than Darwin's finches [Music] foreign