I won’t get into a philosophical argument about the existence or absence of God - the Great Designer, whoever he/she may be. But this amazing planet upon which we live certainly has a set of blue prints upon which species have been drawn up again and again. Welcome one and all to the wonders of Convergent Evolution. This is the process whereby animals will evolve the most efficient shape with which to exploit an ecological niche. A good example can be shown between 3 separate species – Sharks, Mesozoic Ichthyosaurs and Dolphins.
Whilst chatting to a friend in real time in Alaska and enjoying the wonders of our modern technological age, the conversation turned to Moose, the largest deer that currently walks the earth. It is certainly an impressive beast but it got me thinking of other creatures that once roamed this world. Now please excuse me for generalisations and the odd error here and there, I’m no scientist but I want to share my sense of wonder with you.
We are all aware of the end of the Age of Dinosaurs, the Mesozoic Era (250mya to 65mya), encompassing the Triassic, Jurassic and Cretaceous ages, which came to a sudden end with the impact of a comet off the Yucatan peninsula. It allowed small mouse like mammals to emerge from the shadow of the terrible lizards, yet it seemed as if the age of giants was finished.
But as the dust of the comet impact settled, life grabbed at the opportunities on offer. During the 10 million year Paleocene true reptiles became apex predators, thus the world saw giant snakes (Titanboas) and long-legged running crocodiles.
The poor mammals seemed to be subjects of a new dinosaur age as birds, descendants of the kings of old, evolved into the fearsome Terror Birds – flightless 9 feet tall predatory nightmares. But these were evolutionary opportunists, claiming niches in the absence of competitors. Life is a long running programme and efficiency is everything. True, Terror Birds probably preyed on Eohippus – the Dawn Horse – a dog sized Equine, but the mammals had been diversifying. Their teeth became more efficient, their warm blood allowed them to adapt to different climates and in the Eocene epoch they exploded over the world as mammals grew to giant proportions.
But this was an age before the evolution of carnassial teeth, those specialist tools of the cat, bear and dog. Thus Ungulates (hooved animals), the genus of our old friend the Moose and Eohippus evolutionarily split, and split again, to occupy the available ecological niches. This was the age of the Wolfsheep, predators with claws evolved from hooves such as the fearsome Andrewsachus with its huge mouth of predatory teeth.
One of my favourite species for out and out weirdness is the Chaliothere. It’s a horse but like no other, walking on its knuckles. It looks like a gorilla because it once occupied the same niche as present day gorillas do; the wonders of Convergent Evolution.
Eventually efficiency wins every time, especially with the onset of climatic change. Climate change is nothing new, time and again it moves the goal posts, destroying specialists who have adapted themselves into evolutionary cul de sacs and allowing the generalists to expand their range. Alas victims of change included the magnificent 20 tonne Paraceratherium, a giant hornless Rhino that stood some 16 feet tall at the shoulder.
When true carnivores evolved they quickly (in geological terms!) replaced the wolfsheep of old. Carnassial teeth allowed them to process flesh with a greater degree of efficiency. Of course not before an ancient ungulate took to an aquatic lifestyle and gave rise to the Whales and dolphins, including the largest animal ever to have lived (the Blue Whale).
There are some superb modern species which deserve special mention with regard to Convergent Evolution. The Giant Amazonian Otter is 6 feet long. It is no accident that in its territory it actively expels the Cayman, the South American Crocodilian, an animal of similar shape and proportions. Of course if one looks back at the ancient fossil record, when mosses grew as tall as trees in the ancient carboniferous swamps, prior to the evolution of crocodiles, there were huge salamanders occupying the same niche.
While on Madagascar, isolated from other species evolving in Africa, is the Fossa; the largest mammalian carnivore on the island. To all intents and purposes it looks like a cat and eeks out a living as a cat would. However it isn’t a cat at all and is actually a species of Mongoose. Obviously these blueprints must be strictly adhered to, as even the Fossa’s genitalia are shaped, not like a Mongoose’s but more like, yes you guessed it, a cat’s!
It really is a truism that there is nothing new under the sun with Convergent Evolution… but that causes me to ask; why are we unique? In all the millions of years’ worth of evolution are we, Homo Sapiens, a species of primate that began our descent from the trees a million years ago, the only creature that ever occupied our niche? True there were our cousins the Neanderthals, but they were Hominids like us. Why was there never a Saurian hominid?… or was there?!