Darwin's finches show how man harms evolution


They were the birds that were said to have inspired Charles Darwin to formulate his theory of evolution more than 10 years after his famous visit to the Galapagos Islands.

Darwin's finchesiconically depicted how biological diversity and natural selection lead to the origin of new species - but now scientists have detected signs of evolution "in reverse".

Biologists have found that one of Darwin's finches living in the remote Pacific archipelago has begun to revert to an earlier form because of interference caused by a growing human population. Humans are causing evolution to slip into reverse for one of the finch species that lives on the islands. Scientists have found that the finch is losing the distinguishing trait that was causing it to split into two different species - its beak.

The medium ground finch is normally found in two distinct forms - one with a larger beak the other with a smaller one - but when humans come to live alongside the finch, this "bimodal" beak size tends to disappear.

The scientists believe that the arrival of people on the islands may be causing evolution to run in reverse by causing the two extreme versions of the ground finch to revert to individuals with intermediate beak sizes.

In effect, people appear to be unwittingly eliminating the evolutionary disadvantage of having a beak that is half-way in size between the two extremes, according to a study published in the Proceedings of the Royal Society B. As yet the researchers do not understand why people are having this effect but the implications are that the influx of tourists and migrants to the Galapagos is helping to eradicate a source of biological diversity that has made the islands famous.

Professor Andrew Hendry of McGill University in Montreal, who led the study, said: "We need to make more effort to enable those species that are in the process of diversifying to continue to diversify and thereby generate new species. It is appropriate to describe it as evolution in reverse. It's an evolutionary split within a species that is being reversed and we think human activity is responsible," he said.

Darwin collected many dead specimens of the finches on his visit to the islands in 1835 and in 1845 he began to realise that they may have evolved from common stock. He eventually recognised that it was the size and shape of each finch's beak that determined what it could eat and in which ecological niche it was best suited to survive.

"Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends," Darwin wrote in the 1845 edition of the Journal of Researches.

Intermediate beak sizes for medium ground finches are rarely if ever seen in the wild, which indicates that it is usually a disadvantage to be born with an intermediate beak size.

But when the scientists studied populations of medium ground finches living near to human settlements on the island of Santa Cruz, they found that most of them had reverted to having intermediate-sized beaks.

The researchers can only speculate about the causes of the reverse. It could be the result of people introducing alien plants with intermediate-size seeds, or it could be the deliberate feeding of wild birds with imported rice.

"Humans are changing the nature of the adaptive landscape. They are homogenising it. Being intermediate was once bad for the survival of this finch, now it is no longer the case for birds living near people.

"There's plenty of evidence of humans having caused species to go extinct. We're not, in essence, doing anything to reverse the loss of biodiversity," Professor Hendry said.

Have you tried new the Independent Digital Edition apps?
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Guru Careers: Graduate Media Assistant

Competitive (DOE): Guru Careers: We are looking for an ambitious and adaptable...

Guru Careers: Solutions Consultant

£30 - 40k (DOE) + Benefits: Guru Careers: We are seeking a Solutions Consultan...

Guru Careers: Software Developer

£30 - 35k + Benefits: Guru Careers: We are seeking a Software Developer (JavaS...

Guru Careers: Software Engineer / Software Developer

£40-50K: Guru Careers: We are seeking an experienced Software Engineer / Softw...

Day In a Page

Fishing for votes with Nigel Farage: The Ukip leader shows how he can work an audience as he casts his line to the disaffected of Grimsby

Fishing is on Nigel Farage's mind

Ukip leader casts a line to the disaffected
Who is bombing whom in the Middle East? It's amazing they don't all hit each other

Who is bombing whom in the Middle East?

Robert Fisk untangles the countries and factions
China's influence on fashion: At the top of the game both creatively and commercially

China's influence on fashion

At the top of the game both creatively and commercially
Lord O’Donnell: Former cabinet secretary on the election and life away from the levers of power

The man known as GOD has a reputation for getting the job done

Lord O'Donnell's three principles of rule
Rainbow shades: It's all bright on the night

Rainbow shades

It's all bright on the night
'It was first time I had ever tasted chocolate. I kept a piece, and when Amsterdam was liberated, I gave it to the first Allied soldier I saw'

Bread from heaven

Dutch survivors thank RAF for World War II drop that saved millions
Britain will be 'run for the wealthy and powerful' if Tories retain power - Labour

How 'the Axe' helped Labour

UK will be 'run for the wealthy and powerful' if Tories retain power
Rare and exclusive video shows the horrific price paid by activists for challenging the rule of jihadist extremists in Syria

The price to be paid for challenging the rule of extremists

A revolution now 'consuming its own children'
Welcome to the world of Megagames

Welcome to the world of Megagames

300 players take part in Watch the Skies! board game in London
'Nymphomaniac' actress reveals what it was really like to star in one of the most explicit films ever

Charlotte Gainsbourg on 'Nymphomaniac'

Starring in one of the most explicit films ever
Robert Fisk in Abu Dhabi: The Emirates' out-of-sight migrant workers helping to build the dream projects of its rulers

Robert Fisk in Abu Dhabi

The Emirates' out-of-sight migrant workers helping to build the dream projects of its rulers
Vince Cable interview: Charging fees for employment tribunals was 'a very bad move'

Vince Cable exclusive interview

Charging fees for employment tribunals was 'a very bad move'
Iwan Rheon interview: Game of Thrones star returns to his Welsh roots to record debut album

Iwan Rheon is returning to his Welsh roots

Rheon is best known for his role as the Bastard of Bolton. It's gruelling playing a sadistic torturer, he tells Craig McLean, but it hasn't stopped him recording an album of Welsh psychedelia
Morne Hardenberg interview: Cameraman for BBC's upcoming show Shark on filming the ocean's most dangerous predator

It's time for my close-up

Meet the man who films great whites for a living
Increasing numbers of homeless people in America keep their mobile phones on the streets

Homeless people keep mobile phones

A homeless person with a smartphone is a common sight in the US. And that's creating a network where the 'hobo' community can share information - and fight stigma - like never before