I bet, no matter how many years you’ve studied paleontology, it’s still difficult to get excited about a creature that is both strangely shaped and fully encapsulated in history, a monster for many peoples’ enjoyment. But palaeontologist Nick Longrich gets you there. His work is well illustrated, as he puts it in a wry tone, ‘I seek the patterns in history, the fascinating process of macroevolution. I explore how complicated traits arise and how usually remote and highly improbable events like mass extinctions and oceans’ dispersal contribute to this evolution.’
Longrich dares to cross some of the paradigms of his discipline. ‘A fine supposition in individuals working in evolutionary biology is that macro evolution is here just lots and lots of micro evolution, such as what I relate to, almost.’ It wasn’t just evolution that slow and rhythmic, advances Longrich. ‘In a very long time, unusual changes took place. Flight is one, well there has been several instances of the evolution of flight over the ages, but in the last 500 million years, they did it only 4 or 5 times.’ He is fascinated by flight. ‘It is a wonderful adaptation considering that birds are one of the most successful, widespread, diverse and long lived animals – but hollow bones and feathers of birds which are crucial for avian flight evolved but once. Some others, such as bats, insects and some snakes, went half way and developed other ways to fly.’ So even as you are thinking of the attractive features of flying snakes, Longrich goes on, ‘But the evolution of avian flight was an extraordinary event.’
One needed the right adaptations, of things happening in the right order, the most appropriate environment, the most suitable ecological niches. Everything had to fall into place or it couldn’t happen — that is defining improbability or unpredictability.’
Fossils of flying birds date from the Jurassic period. Longrich describes, ‘First, it was probably just the dinosaurs, hopping from branch to branch. To balance, they would probably spread their shoulders like a free fall parachutist. It would allow them, in a way, to slow their drop. Next, the integument including feathers and skin might have developed to assist the control of downward movement in a better manner. We see an incipient version of this in squirrels actually which have some membrane on their arms. That’s when feathers came into play and evolution began to act on them.
Already the dino feathers you are picturing would have had some ragged edges. Longrich however cautions: In the first sense, these would be rather simple,’ These would have been more of fur than feathers like those of birds. Pragmatically, these would be covered to avoid excessive loss of heat. But when huddled together, like wayward floozies over a bedpost, they would help control the direction and descent. By getting bigger, species would be able to lift in an angle, meaning you will be able to come down but not just ‘down’, it would be ‘down and forward’ in a standing posture in soaring area.
Within due course, the animals would also gain the ability to control landing – they’d possess large structures at the tail base for this like how an arrow advances in flight. We know that squirrels have a big bushy tail – this is an aerodynamic stabiliser which prevents them from tumbling over. This perhaps suggests that dinosaurs too evolved a large ornated tail as they passed through the gliding stage and finally, the flapping stage.’
Once more, the chances of all this happening were slim. Longrich states, ‘The primary mode of tree-dwelling was gliding between the trees but then dinosaurs came about who ‘flapped’ their wings to fly. More than one attempt was made to achieve flight by the dinosaurs. A Chinese fossil that was on the contrary discovered had the gliding membranes but not the wings as those of a bird, this could be a derivation of an adaptation that fossil species did not expand best additional out. While they were at it, more than one evolutionary line of the dinosaurs got the chance of a lifetime.’
‘The archaeopteryx is an ancestor to today’s birds,’ he says, ‘It is regarded to have lived around one hundred forty-five million years ago. The bone structure is dinosaur-esque, it is like a miniature velociraptors but with more avian features. This has very advanced plumage. The wings were extension with pointed wing tips and tail with feathers, and hind limb with small feathers that could function like extra appendages. And so it did flap these wings and flew,’ Longrich hesitated then continued, ‘Though not very well but it did.’
He talks about the course which he pursued with the Archaeopteryx fossil: ‘Material reconstruction of the wings in the most intricate and precise details was the aim’.
So, I began to draw, stroking my pencil and drawing in every shaft and structure in order from strand to strand – at which point I realized that a lot of the traditional restoration was not applicable. Contains everybody these series of feathers that interlace with the wing feathers? They were so systematic. Why was every other feather tucked in, rather than just one or two? What were those other wings like? I discovered that instead of looking at two series of feathers – one was the feathers forming the outer walls of the body. The other was the primary covering feathers. ’ Longrich is heard with a hint of exasperation, ‘But then you feel it, when you sit down and draw something, the fossil has no choice, you have to move the fossil and not put your concepts on the fossil.’
Birds started their evolutionary journey from the mid-Jurassic period. It took time. In fact, it took millions of years to perfect the genetic mutations necessary. ‘Meanwhile,’ Longrich says, almost in one breath, ‘There was a big extinction event in the Triassic and another in the later Jurassic periods. All of these events too resulted in variations. This is when some of the most remarkable changes seem to occur relative to evolution. A pattern of evolution begins in the aftermath of mass destruction. It was after the period dominated by the asteroid that wiped most dinosaurs out that the bats evolve. ‘Then there were the mammals.’
‘As birds evolved, which were descendants of dinosaurs, their wings became more diverse,’ The theropod clade caused a great diversification among the other small animals which had wings. “Some of them are extraordinary in size. For example, the albatross has very long wings. Most of the wing of a duck cannot be seen. Others are adapted for gliding, others for plunging to the depths of the ocean. Others are even for fighting – there are some aggressive plovers with stabbing spikes on their wings and geese with knobs to punch with. ‘Evolution can be such fun,’ Longrich smiles kindly. The two prehistoric features evolved for one purpose, morphography seeking for construction or decoration, ended up being used for toy-making. ‘ Except for outer structures, the edifice of bird’s wings has remained constant for the last hundred million years.’ ‘He adds – there is an archaeopteryx from the Jurassic closer in shape to a wing of a modern bird than any other prehistoric creatures. In its retention, the plumage is rudimentary, but in a few more million years you would have had practically a modern avian wing. It could be that the wings of a bird we see today are relics of evolution – there is not much change in sight. That was because it was as efficient as it could get.’
