Dinosaurs may have evolved wings to attract mates

Galvasean

Kind of a biased study/article to be honest. It makes the impression that the 'trees down' theory is not well supported by the fossil record when in fact it seems to be.
Interesting read though.

http://www.telegraph.co.uk/scienceandtechnology/science/dinosaurs/5105218/Dinosaurs-may-have-evolved-wings-to-attract-mates.html

Richard Gray wrote:

Dinosaurs may have evolved the ability to fly as a way of impressing the opposite sex, according to biologists.

The evolution of flight by dinosaurs, widely accepted as the ancestors of modern birds, has been a controversial subject among palaeontologists for decades.

While some believe avian dinosaurs learned to fly by jumping out of trees and gliding to the ground, almost all of the bird-like ancestors found as fossils were ground-dwelling creatures.

Instead scientists have suggested that these "proto-birds" flapped their forelimbs like wings to give them additional thrust to help them climb while attempting to escape from predators.

New research from the University of Manchester, however, suggests this is inefficient and reduces the ability of the animals to run fast.

The biologists claim there would have been little competitive advantage that could have driven natural selection of wings in this way.

Rather, they suggest another evolutionary force was at work, a procesdins known as sexual selection, where traits deemed as attractive by the opposite sex become more common and more pronounced through generations because they are favoured by mating animals.

Dr Robert Nudds, a biologist at the University of Manchester who carried out the research, said his work had raised the prospect that sexual selection played a bigger role in the evolution of flight than had been previously thought.

He said: "The problem we see is why an animal would start holding its forelimbs out to the side in a symmetrical manner in the first place.

"Two legged animals use their forelimbs in asymmetrical movements to help counteract the force fro the legs and to stop their body from rotating as they run.

"If an animal started running with its limbs held out to the side, then there would be cost that would have left them competitively at a disadvantage. There must have been another factor involved to allow this trait to continue through the generations.

"One theory is that these feathered dinosaurs used their forelimbs in some sort of sexual display, so maybe they ran around with their arms outstretched to show off how pretty their feathers were."

Early birds are first thought to have appeared during the late Jurassic period around 145 million years ago. Fossils have been found of a feathered dinosaur, known as Archaeopteryx, which is thought to have been a stepping stone between dinosaurs and modern birds.

Dr Nudds, who worked with palaeontologist Dr Gareth Dyke at University College Dublin, used biomechanical models to simulate how Archaeopteryx and two other feathered dinosaurs, Caudipteryx and Protarchaeopteryx, would have moved.

They found that the early wings of these animals would have provided little thrust to assist when running uphill and would have also increased drag.

Dr Nudds added: "To me, it makes more sense that dinosaurs began to hold their forelimbs out when jumping out of trees and eventually started gliding to the ground, but the problem is the evidence in the fossil record doesn't support this.

"There may of course be gaps in the fossil record and with the ground dwelling species we have discovered so far, it seems that something other than simple natural selection drove the evolution of symmetrical forelimb posture."

Dr Paul Barrett, a palaeontologist at the Natural History Museum where a specimen of Archaeopteryx is held, said: "This is a controversial topic.

"I find the idea that proto-birds flapped their forelimbs to help them climb trees quite attractive, but it is one of a number of ideas that are out there and I suspect the truth will be a combination of a number of these."

image by Todd Marshall