Post by Wayne Smith on Dec 9, 2020 18:14:04 GMT 10
Two new articles on Darwin's evolutionary theories.
Sticking a neck out for evolution: Is Darwin's theory about long-necked giraffes true?
Charles Darwin was the first to propose that giraffes evolved into the elegantly long-necked creatures they are because successive generations realised that extra vertebrae helped them get access to tender leaves on top of trees. Pretty smart thinking by giraffes — and Darwin, of course, for deducing this millennia later.
But, then, thanks to an epiphanic moment while seeing two male giraffes using their necks to fight over a female, a researcher concluded in 1997 that the main purpose of that elongated scrag was not food but sex. In other words, size (of the neck) matters. While the theory may have its adherents, what Darwin posited about giraffes was probably right after all, going by recent discoveries.
Scientists now aver that a sauropod called Bagualia alba that roamed Argentina 179 million years ago developed not only its huge teeth but also a strong, long neck to reach and chew the tough leaves of tall conifers, the only trees that proliferated after volcanic eruptions raised temperatures.
That the extension proved useful is evident as successive herbivorous dinosaurs continued with this natural equipment. Humans resort to technology rather than evolution —like using a ladder rather than waiting for necks or limbs to lengthen. Without this trait of jugaad and innovation, we may have evolved very differently indeed.
Charles Darwin was right about why insects are losing the ability to fly
Most insects can fly.
Yet scores of species have lost that extraordinary ability, particularly on islands.
On the small islands that lie halfway between Antarctica and continents like Australia, almost all the insects have done so.
Flies walk, moths crawl.
"Of course, Charles Darwin knew about this wing loss habit of island insects," says PhD candidate Rachel Leihy, from the Monash University School of Biological Sciences.
"He and the famous botanist Joseph Hooker had a substantial argument about why this happens. Darwin's position was deceptively simple. If you fly, you get blown out to sea. Those left on land to produce the next generation are those most reluctant to fly, and eventually evolution does the rest. Voilà."
But since Hooker expressed his doubt, many other scientists have too.
In short, they have simply said Darwin got it wrong.
Yet almost all of these discussions have ignored the place that is the epitome of flight loss - those 'sub-Antarctic' islands. Lying in the 'roaring forties' and 'furious fifties', they're some of the windiest places on Earth.
"If Darwin really got it wrong, then wind would not in any way explain why so many insects have lost their ability to fly on these islands," said Rachel.
Using a large, new dataset on insects from sub-Antarctic and Arctic islands, Monash University researchers examined every idea proposed to account for flight loss in insects, including Darwin's wind idea.
Reporting today in Proceedings of the Royal Society B, they show that Darwin was right for this 'most windy of places'. None of the usual ideas (such as those proposed by Hooker) explain the extent of flight loss in sub-Antarctic insects, but Darwin's idea does. Although in a slightly varied form, in keeping with modern ideas on how flight loss actually evolves.
Windy conditions make insect flight more difficult and energetically costly. Thus, insects stop investing in flight and its expensive underlying machinery (wings, wing muscles) and redirect the resources to reproduction.
"It's remarkable that after 160 years, Darwin's ideas continue to bring insight to ecology," said Rachel, the lead author of the paper.
Professor Steven Chown, also from the School of Biological Sciences, added that the Antarctic region is an extraordinary laboratory in which to resolve some of the world's most enduring mysteries and test some of its most important ideas.
Sticking a neck out for evolution: Is Darwin's theory about long-necked giraffes true?
Charles Darwin was the first to propose that giraffes evolved into the elegantly long-necked creatures they are because successive generations realised that extra vertebrae helped them get access to tender leaves on top of trees. Pretty smart thinking by giraffes — and Darwin, of course, for deducing this millennia later.
But, then, thanks to an epiphanic moment while seeing two male giraffes using their necks to fight over a female, a researcher concluded in 1997 that the main purpose of that elongated scrag was not food but sex. In other words, size (of the neck) matters. While the theory may have its adherents, what Darwin posited about giraffes was probably right after all, going by recent discoveries.
Scientists now aver that a sauropod called Bagualia alba that roamed Argentina 179 million years ago developed not only its huge teeth but also a strong, long neck to reach and chew the tough leaves of tall conifers, the only trees that proliferated after volcanic eruptions raised temperatures.
That the extension proved useful is evident as successive herbivorous dinosaurs continued with this natural equipment. Humans resort to technology rather than evolution —like using a ladder rather than waiting for necks or limbs to lengthen. Without this trait of jugaad and innovation, we may have evolved very differently indeed.
Charles Darwin was right about why insects are losing the ability to fly
Most insects can fly.
Yet scores of species have lost that extraordinary ability, particularly on islands.
On the small islands that lie halfway between Antarctica and continents like Australia, almost all the insects have done so.
Flies walk, moths crawl.
"Of course, Charles Darwin knew about this wing loss habit of island insects," says PhD candidate Rachel Leihy, from the Monash University School of Biological Sciences.
"He and the famous botanist Joseph Hooker had a substantial argument about why this happens. Darwin's position was deceptively simple. If you fly, you get blown out to sea. Those left on land to produce the next generation are those most reluctant to fly, and eventually evolution does the rest. Voilà."
But since Hooker expressed his doubt, many other scientists have too.
In short, they have simply said Darwin got it wrong.
Yet almost all of these discussions have ignored the place that is the epitome of flight loss - those 'sub-Antarctic' islands. Lying in the 'roaring forties' and 'furious fifties', they're some of the windiest places on Earth.
"If Darwin really got it wrong, then wind would not in any way explain why so many insects have lost their ability to fly on these islands," said Rachel.
Using a large, new dataset on insects from sub-Antarctic and Arctic islands, Monash University researchers examined every idea proposed to account for flight loss in insects, including Darwin's wind idea.
Reporting today in Proceedings of the Royal Society B, they show that Darwin was right for this 'most windy of places'. None of the usual ideas (such as those proposed by Hooker) explain the extent of flight loss in sub-Antarctic insects, but Darwin's idea does. Although in a slightly varied form, in keeping with modern ideas on how flight loss actually evolves.
Windy conditions make insect flight more difficult and energetically costly. Thus, insects stop investing in flight and its expensive underlying machinery (wings, wing muscles) and redirect the resources to reproduction.
"It's remarkable that after 160 years, Darwin's ideas continue to bring insight to ecology," said Rachel, the lead author of the paper.
Professor Steven Chown, also from the School of Biological Sciences, added that the Antarctic region is an extraordinary laboratory in which to resolve some of the world's most enduring mysteries and test some of its most important ideas.