Seeing evolution in action


Peter and Rosemary GrantThe pop-science notion is that evolution takes a long time. Millennia, many millennia; even millions of years. But is that always true? Can one actually see and measure evolution in action? Can it happen in such a short time as to be recorded?

Peter and Rosemary Grant say they have. And it’s the subject of a new book they co-authored based on their research.

Their story was reported in the April 23 issue of the Princeton Alumni Weekly. It’s a terrific read if for nothing more than their 40-year tale of dedication, science and adventure on the isolated Daphne Major Island, one of the smaller islands of the Galapagos chain.

Forty years studying finches together, away from human company, away from the comforts of civilization. The small birds that first gave Charles Darwin insight into the mechanics of natural selection were their focus. And the Grants report they have seen that mechanism in action on the island.

Scientists previously had reported seeing the processes of natural selection among bacteria, honeycreepers, cichlid fish, and fruit flies. As Peter Grant puts it, “Until we began, it was well understood that agricultural pests and bacteria could evolve rapidly, but I doubt that many people thought that about big, vertebrate animals.”

The Grants believe that hybridization is an important force in the rise of new species, and think this applies, too, to human evolution. For a long time, for example, paleontologists believed that Neanderthals and “modern homo sapiens” did not interbreed when they came into contact in prehistoric times, but recent research indicates that about 20 percent of Neanderthal genes have been preserved in our species. “It’s almost been a hobbyhorse of ours,” Peter says. “We were saying, ‘I bet there has been gene exchange between the lineages of homo sapiens throughout their evolution.’”

The Grants’ new book is targeted at both lay readers and scientists familiar with their work, and broadly discusses their findings about natural selection, hybridization, population variation (why do some populations of birds vary more dramatically in beak size?), the potential vanishing of a species through interbreeding, and, of course, the potential origin of a new species — the Big Bird lineage. They also touch on global warming and its possible effect on Darwin’s finches. Most of all, the book is an affirmation of the importance of long-term fieldwork as a way of capturing the true dynamism of evolution.

The Grants’ claim isn’t the first such, nor likely to be the last. There are numerous examples of evolutionary action recorded in the annals of in biology. Listverse has eight of them, some of which are textbook examples:

  • The Peppered Moth
  • Live Birth in Three-toed Skinks
  • The Arms Race between Crabs and Mussels
  • Italian Wall Lizards
  • Cane Toads
  • Darwin’s Finches
  • Butterflies and Parasites
  • Evolution in the Lab (antibiotic-resistant pathogens)

Each an interesting case that underscores the proof of evolutionary theory. But there are others. Blind mole rats are a likely candidate. As Science reported:

Blind mole rats could be a real eye-opener for evolutionary science. According to a new study, the burrowing rodents are key to answering a controversial question about how new species arise.

And American cliff swallows:

The American cliff swallow is best known for its yearly migration between North and South America, traditionally resulting in the annual return of the swallows to Mission San Juan Capistrano in Southern California on March 19. Now it seems they also provide a lesson in the workings of natural selection. A three-decade long study carried out by a husband and wife ornithological team in western Nebraska has, thanks to long years of carefully recording all available data, shown that roadkill has exerted a selective advantage on swallows with shorter wingspans.

And then there are grasshoppers changing their song in response to technology:

Grasshoppers collected from roadside populations produced songs with low pitches that were slightly higher than the low pitches produced by grasshoppers from quiet fields. The biologists hypothesize that this shift enables roadside females to distinguish the low pitches in the males’ calls from ambient noise.

Stickleback fish and sockeye salmon, too. The list is rich in examples.

Viruses in particular show remarkably fast evolution. So do some bacteria. As the NPR reported in 2013, a 25-year-old experiment with bacteria shows just how effective a force natural selection is. After 50,000 generations,

It turns out, though, that the bacteria haven’t stopped evolving, and it looks like they never will, according to a report Lenski’s group has now published in the journal Science.
Lenski, along with colleagues Michael Wiser and Noah Ribeck, dug into a freezer that holds samples of the bacteria that were taken every few months over the course of the whole experiment. The researchers can pull out, say, the 10,000th or 40,000th generation and bring these frozen bacteria back to life.
“We can actually compete organisms that lived at different points in time, so we can compete the evolved bacteria head to head against their ancestors,” says Lenski.
What they’ve found is that the bacteria just keep getting fitter and fitter and fitter. The pace of improvement is slowing down, but shows no sign of stopping.

However, whether this is just adaptation or evolution has been much debated*.

The New York Times ran a fascinating piece on bacterial evolution in 2013. It noted:

To better understand how the bacteria swarm, Dr. Xavier and his colleagues allowed them to evolve. They seeded petri dishes with a few hundred microbes and gave them a day to swarm and reproduce. The next day, they drew a small sample of the bacteria from the dishes and used them to seed new ones.
The scientists reasoned that, with each generation, new mutations would arise from time to time. If a mutation helped bacteria thrive in this new environment, it might become more common because of natural selection.
And so it did.
Within a few days, the evolution of the bacteria took a dramatic turn. The bacteria became 25 percent faster than their ancestors — Dr. Xavier dubbed them “hyperswarmers.” A movie of hyperswarmers starkly illustrates how different they had become, able to fill up the entire dish.

It’s impressive to watch the videos of normal bacterial behaviour and that of the evolved “hyperswarm.”

The fossil record is replete with examples of evolutionary progress, too, and modern science has contributed to a fuller appreciation and understanding of evolution through new technologies and techniques. We have many lineages well-mapped through the fossil record – and scores of transitional fossils – including the human line.

The Grants’ book is not merely a textbook or a description of 40 years studying birds. The article calls it,

…an affirmation of the importance of long-term fieldwork as a way of capturing the true dynamism of evolution.
“Perhaps the biggest contribution of the Grants’ work is simply the realization not only that evolution can be studied in real-time, but that evolution doesn’t read the textbooks,” observes Jonathan Losos, a Harvard evolutionary biologist.

I look forward to reading it.

April is a fitting month for this story: Charles Darwin, the father of evolutionary theory, died on April 19, 1882; four years younger than the Grants are now. A life well-lived.

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* Debated mostly by creationists who disregard the science behind natural selection in favour of a supernatural or magical answer – so let’s put the creationists aside because they can’t contribute to the discussion in a meaningful way.