Understanding the Evolution of Flightless Birds

Source: National Geographic News Report 5/13/14

One of the stronger evidences for evolution is the existence of such creatures as flightless birds.  If one were creating creatures willy-nilly all at once, as creationists assert, why create a creature with wings and feathers but without the ability to fly?  It makes no sense from a creationist perspective, but it makes perfect sense in an evolutionary perspective. 

Scientists, however, are always interested in the details of evolution.  Where does each known creature, past or present, fit in the evolution of life?  This article focuses on a puzzle that evolutionary biologists have been pondering for 150 years: where to place the creatures known as tinamous, a South American bird that has limited ability to fly.  It shares some similarities with flightless birds such as emus, ostriches, and kiwis.  Did it evolve from creatures like these, redeveloping the ability to fly?  Such a scenario is unlikely.  But it is equally unlikely that they would independently evolve other similar features to the flightless birds, known collectively as ratites.

In the past, such questions could not be answered conclusively because the evidence of morphology (body features of existing creatures) and fossil evidence can only suggest possible avenues of evolution.  The ability to sequence DNA now provides an independent means of analyzing ancestry and a new study has done just that with the DNA of flightless birds and the tinamous.

Science advances using the scientific method.  This method tests a hypothesis by stipulating what results would be expected in an experiment if the hypothesis were true.  Then if the tests show the expected results, it supports the hypothesis.  Results that are at odds with what is expected cast doubt on the hypothesis.

This study produced evidence from DNA that supports the hypothesis that the flightless birds and tinamous share a common ancestor that could fly.  The fact that DNA evidence allows us to confirm a connection suggested by morphology and fossils adds to the existing mountain of evidence that evolution is a fact, not a hypothesis still being tested, as anti-evolution critics would have us believe.

Is Evolution Predictable?

Source: Sciencemag.org news report 5/15/14

This report highlights something that anti-evolutionists need to recognize: scientists no longer debate whether evolution happens or not; they instead are interested in how evolution works.  Furthermore, the science has developed to the point where experiments can shed light on whether or not evolution is predictable.  The report describes research into the mechanism of evolution using an insect that evolved to resemble a leaf on a plant. 

So Patrik Nosil, an evolutionary biologist at the University of Sheffield in the United Kingdom, turned to a stick insect called Timema cristinae. In many places in California, this species has split into two forms, or ecotypes, on a hillside. One form is wide and lives on a wide-leaf plant; the other is narrow, with a stripe down its back, and lives on a plant with narrow leaves. Nosil and his colleagues sequenced the genomes of dozens of individuals of each ecotype from multiple hillsides to assess the genetic differences that arose to make them specialized for their particular host plant.

The report goes on to describe the following experiment:

Nosil’s team transplanted hundreds of individual stick insects onto the plant they weren’t adapted to and collected the offspring a year later. They checked the offspring’s DNA to see how the frequency of different versions of their genes shifted compared with those frequencies in the parents. Such shifts represent places where one version provides a better survival advantage than another, enabling the insects with that version to reproduce. Dozens of those shifts coincided with the DNA differences between the ecotypes, signaling that those differences were due to selection, not chance.

Experiments such as this are common in biology today.  They contradict the commonly repeated assertion by anti-evolutionists that evolution cannot be tested.  In fact, thousands of experiments have been conducted which, like this one, show the process of evolution in experiments.  The ability to sequence DNA adds another layer to the understanding of evolution, since the DNA is the physical link that makes evolution possible. 

Did the Evolution of Animal Intelligence Begin With Tiktaalik?

Source: Smithsonian Magazine June 2014

Another of the notorious (to the anti-evolution crowd) gap in the fossil record gets filled.  As discussed in earlier posts, fossil gaps are not evidence of any alleged failure of evolutionary theory.  Gaps are to be expected because fossils only form in special environments.  We also haven't found all the fossil beds that do exist.  So we should expect to find fossils which fill gaps.  In this case we have an important link between land and sea creatures.

Quoting from the Smithsonian Magazine article:

In 2004, when the fossil bones of Tiktaalik roseae were dug from the ground of Ellesmere Island, in the Canadian Arctic, the discovery was hailed as a breakthrough not just for paleontology, but for beleaguered science teachers trying to keep creationism out of their classrooms. A fish (with scales and gills) clearly resembling a tetrapod (with a flat head, a neck and prototypes of terrestrial limb bones in its lobelike fins), it precisely filled one of the gaps in the fossil record that creationists cited as evidence against Darwinian evolution.

The article goes on to show how science always learns from new data such as this. 

 The hip and pelvis were surprisingly robust, suggesting more powerful rear limbs than previously believed. Although almost certainly still encased in fleshy lobes, appendages could have helped support or even propel the animal in shallow water or mud flats. If so, it changes our view of the evolution of tetrapods, whose ancestors were believed to drag themselves by their forefins, only developing useful hind legs once ensconced on land.

The article also comments on the underlying assumption of evolution, that new species evolve when there is a new environment to exploit.  At the time the ocean had large carnivorous predators a-plenty, such as Taktaalik.  But the land had a diverse range of plants and some animals such as mollusks and insects with no predators of any size.  Getting out of the ocean also put a creature out of reach of the predators of the sea. 

As for what drove this epochal migration, “it’s extremely bloody obvious: There were resources on land, plants and insects, and sooner or later something would evolve to exploit them,” says vertebrate paleontologist Mike Benton of the University of Bristol. It’s also possible, says Shubin, that fear played a part. “If you look at the other fish in the water at the time, they’re big monstrous predators,” he says. Some exceeded 20 feet in length. Even for Tiktaalik, a toothy carnivore itself, this was a “predator-rich, competitive environment.” If you can’t be the biggest fish in the pond, maybe it’s better to get out of the water altogether.

In 2004, when the fossil bones of Tiktaalik roseae were dug from the ground of Ellesmere Island, in the Canadian Arctic, the discovery was hailed as a breakthrough not just for paleontology, but for beleaguered science teachers trying to keep creationism out of their classrooms. A fish (with scales and gills) clearly resembling a tetrapod (with a flat head, a neck and prototypes of terrestrial limb bones in its lobelike fins), it precisely filled one of the gaps in the fossil record that creationists cited as evidence against Darwinian evolution.


Read more: http://www.smithsonianmag.com/science-nature/evolution-animal-intelligence-begin-tiktaalik-180951428/#JKOFTChzSBtmzOz2.99
Give the gift of Smithsonian magazine for only $12! http://bit.ly/1cGUiGv
Follow us: @SmithsonianMag on Twitter

In 2004, when the fossil bones of Tiktaalik roseae were dug from the ground of Ellesmere Island, in the Canadian Arctic, the discovery was hailed as a breakthrough not just for paleontology, but for beleaguered science teachers trying to keep creationism out of their classrooms. A fish (with scales and gills) clearly resembling a tetrapod (with a flat head, a neck and prototypes of terrestrial limb bones in its lobelike fins), it precisely filled one of the gaps in the fossil record that creationists cited as evidence against Darwinian evolution.


Read more: http://www.smithsonianmag.com/science-nature/evolution-animal-intelligence-begin-tiktaalik-180951428/#JKOFTChzSBtmzOz2.99
Give the gift of Smithsonian magazine for only $12! http://bit.ly/1cGUiGv
Follow us: @SmithsonianMag on Twitter