Longrich challenges some of the established wisdom in his field. ‘A standard view in evolutionary biology is that macro evolution is just the result of lots of micro evolution – I question that.’ Longrich argues that evolution did not happen on its own and in a rhythmic way. ‘Over very long time spans, unusual things happened. For example, the evolution of flight happened over and over again, but in the last half billion years, it happened only four to five times.’ He describes the wonder of flight. ‘It’s an amazing adaptation, given that birds are very successful creatures, widespread, diverse and long-lived – but bird flight evolved only once. Some other things evolved flight, such as bats, insects and some snakes that went halfway.’ When you consider the fascination of flying snakes, Longrich adds, ‘But Bird evolution Flight was extremely rare to occur. You needed the right adaptations, occurring in the right order, the most favorable environment, the right ecological niche. Everything had to be aligned or it couldn’t happen – there’s impossibility or unpredictability involved.’
I can do that too! Squirrels can fly to some extent using their arms and bushy tails (Photo: Getty Images and iStock)
Avian flight has its roots in the Jurassic era. ‘At first, probably only Dinosaursjumping between branches. To stabilize themselves, they probably threw their arms out to the side, like a skydiver. This would allow them to descend slowly. Next, the dermal covering, Wing And the skin could have expanded to create larger surfaces that could control descent more effectively. We actually see an early version of this in squirrels that have some membranes on their arms. Evolution could then start to expand with wings.’
then and Now: Archaeopteryx The fossil (above), the first bird at 145 million years old, was discovered in Germany in 1861 – showing a full set of feathers, it is not very different from birds seen today, such as the hoatzin (R) (Photo: Getty Images and iStock)
Dinosaur feathers may not have looked very polished. ‘In the beginning, they would have been quite crude,’ explains Longrich. ‘Rather than bird feathers, they would have been more like hairs, mostly for insulation. But packed together, like the gathered bristles of a paintbrush, they would have allowed you to control landing and changing direction. As they got larger, species could generate enough lift to land at an angle – so, you’re not just coming down, you’re doing so and moving forward. Creatures would have also developed control over landing – they would have had large structures on their tail to stabilize it, like the flight of an arrow. Squirrels have a large bushy tail – it’s an aerodynamic stabilizer that prevents them from falling over. Dinosaurs would have probably developed a large bushy tail as well, with gliding and flapping at the end.’
Again, the likelihood of this happening was very low. ‘Dinosaurs started out by gliding between trees – then, a lineage evolved that could flap its wings,’ says Longrich. Dinosaurs probably experimented with flight more than once. One fossil found in China has gliding membranes, but these are not like those in birds – this may have been an independent evolution that didn’t go ahead. When they did the experiment, only one lineage of dinosaurs got lucky.’
Longrich’s own research on Archaeopteryx has been pioneering.
(Photo: Getty Images and iStock)
‘Archaeopteryx is an early bird,’ he describes, ‘It’s 145 million years old. The skeleton is similar to that of a dinosaur, almost like a non-avian Velociraptor, but smaller. It has very modern feathers. It has pointed wings, tail feathers, and little feathers on the hind legs that act like a pair of extra wings. It could fly by flapping its wings,’ Longrich pauses, then emphasizes, ‘maybe not very well, but it could fly.’
Describing his study of the Archaeopteryx fossil he says, ‘I wanted to reconstruct the feathers in great detail. So, I started drawing every branch and structure one by one – then I realised that much of the traditional reconstruction wasn’t working. You had these series of feathers that alternated with wing feathers. They were too regular. Why was every other feather displaced, not just one or two? How did everything else about these feathers look right? I found that we were actually looking at two separate series of feathers – one was the main wing feather. The other was the coverts.’ You can hear Longrich’s amusement when he says, ‘When you sit down and draw something, it forces you to let the fossil speak, rather than imposing your preconceptions on it.’
The evolution of birds began in the middle Jurassic period. The process was slow, it took time to get the right mutations – millions of years. ‘Meanwhile,’ Longrich adds enthusiastically, ‘there was a big extinction event during the Triassic period and another in the later Jurassic. All of these also led to diversity. This is the period when we see evolution at its most recent – things start to move forward after a mass extinction. After the asteroid impact that wiped out most of the dinosaurs, bats began to evolve. Then came mammals.’
As birds, the successors of dinosaurs, evolved, their feathers also diversified. ‘There’s a huge range of feathers now. Some, like the albatross, are very long. Ducks have really short wings. Some are specifically for soaring, some for diving. Some are even used as weapons, for example, some plovers have stabbing spurs on their wings while geese have knobs on their wings for punching. With evolution,’ Longrich says, smiling gently, ‘a feature might evolve for a certain purpose – but then, it turns out to be useful for something else too.’ Still, the basic arrangement of bird feathers hasn’t changed much in the past 100 million years. ‘The Jurassic Archaeopteryx has something very close to a modern bird’s wing,’ says Longrich. The feathers are primitive but in a few more million years, you’ll have basically a modern bird’s wing. So, a bird’s feather today is actually a living fossil – it hasn’t changed much. That’s because it’s as good as it can be.’
I’m really convinced: the cool thing is that bird feathers haven’t changed much in over 145 million years. (Photo: Getty Images and iStock)
