How did different species come about in the animal kingdom?

Birders often argue vociferously over the identity of certain birds – like those notorious ‘little brown jobs’ – the warblers, many species of which resemble each other so closely that frankly only a DNA analysis would accurately pinpoint their identity. What astonishes me, however, is how all these different species came about in the first place and this holds true not only for similar looking birds but of every living creature on the planet.

Let’s take three of India’s commonest parakeet species (there are more, which I’m leaving out to keep things simple), the Alexandrian, the rose-ringed and the plum-headed parakeet. At one point of time, they (and the other parakeets not mentioned here) must have had a single grandparent parakeet. And many, many years down the line, at least three of its grandkids developed separately into these three species of parakeets that would not have anything to do with each other – especially have babies. The Alexandrian, the largest of the trio, wears maroon epaulettes on its shoulders, has a huge red nutcracker bill, squawks raucously, and flies with more deliberation than its other cousins. It is also harnessed by conmen into forecasting your future and is a popular (if illegal) pet. The rose-ringed is our commonest parakeet, streaking across the skies screaming like a squadron of airborne green chillies. The plum-headed, has a head the colour of plum (the ladies have grey heads) and is smaller. They rocket around leaving a whistling tooi-tooi query in its wake. So why and when did these three parakeets begin to go their different ways considering their common ancestor?

parakeets Rose-ringed parakeet (Photo: Ranjit Lal)

Darwin faced this same question in the Galapagos Islands when he discovered that different islands in the archipelago had their own unique species of finches – all of which had the same great-great to the power of X grandparents. Volcanic eruptions caused the formation of the islands, separated from each other by the sea, each with a colony of finches that survived the upheaval. Over time (many of thousands of years), the finches on each island settled down and subsisted on what those islands could provide for them. In some cases, it was nuts and seeds, in others nectar-yielding flowers. So the finches living on the nuts and seeds gradually developed, through natural selection, beaks that were tailor-made for nut-cracking, and those that developed on the nectar-providing islands, developed bills that were long and needle-like so they could probe the depths of the flowers. If these two varieties were to meet, they would really not be able to go on a dinner date (“What? You eat nuts? You must be nuts!”), much less go any further. Both had changed so much that they had become individual species.

Another famous example given for speciation due to geographic (and geological) factors is that of the antelope squirrel (which looked so much like our own local squirrel it startled me!) of Colorado. Way back when the mighty Colorado River was a happily tinkling little thing, the antelope squirrel lived on either shore, possibly hopping across on river rocks or fallen trees to meet up with friends and relatives on the opposite side. Then the Colorado River began gouging out what ended up being the Grand Canyon, and the squirrels on the northern banks of the river could no longer get across to their cousins on the southern banks and vice-versa. Over thousands of years, each developed into its own species: the southern bank dwellers were called the Harris’s antelope squirrel, the northern bank dwellers were called white-tailed antelope squirrels. Though they still looked pretty similar, their genetic profiles no longer matched and even if they did eat the same food, they could not go beyond a good-night kiss after a date (“Sorry, it’s not you, it’s me!”).

This kind of ‘speciation’ due to geographic factors has been called allopatric speciation: ‘allo’, meaning other, and ‘patric’ home: other home. Sometimes, a small group of individuals breaks away from a larger group and forms its own isolated (again by geography) clique ultimately forming its own species. This is called peripatric speciation. In what seems like scientists splitting hairs, there is parapatric speciation in which groups separate and spread over large areas, this making it difficult for one group to interact with (let alone mate with) another, as each group adapts to its own environment and resources.

There is also the controversial sympatric speciation (which some scientists don’t believe in) where new species develop without any geographic separation involved. The cichlid fish of East Africa’s Lake Nyasa (aka Lake Malawi) — nearly 1,000 species strong have often been cited as an example: where species developed due to sexual selection and ecological factors. Some lady cichlids may have taken a shine to gentlemen cichlids, say with a certain attitude, or dazzling scale markings, and gone with them: their babies would have inherited the same preferences and, over generations, a new species came about, with these mainstream traits. When there are a thousand cichlid species swimming around, it is difficult to pinpoint with any certainty which one was the species that started the ball rolling – which is why scientists are dubious about this theory.

Finally, there’s also artificial speciation, where it is us human beings fiddling with the genetic structure of say fruit flies, to develop new species (generally we have a selfish motive for this).

But what is wonderful is that for every living creature, there must be a fascinating back-story as to how, why and when it became what it is today. There really are a zillion untold stories out there.

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