Tuesday, 5 February 2008

The chicken or the egg?

Sitting in KFC and with chickens on the mind I started to ponder the old conundrum: what came first the chicken or the egg?

Okay let’s take it logically:

The egg was laid by a chicken which itself came from an egg etc etc ad infinitum. An infinite regress as the mathematicians would say. But hold on a sec – if every chicken comes from an egg, then surely the egg came first?

But if so, who laid the first egg?

So there seems to be no answer. But of course there is. Since there MUST be an answer. After all, the chickens today didn’t come from nowhere did they?

Well, that’s the whole thing really. Cos it’s a trick question. Since there is no such thing as A chicken. And there is no such thing as AN egg. In other words, a chicken today is very different from one 5,000 years ago, and compared to one 500,000 years ago, you probably wouldn’t recognize it as the same thing.

Here’s the scientific explanation from Wikipedia:

According to the principles of speciation, neither the chicken nor the egg came first, because speciation does not occur in simple, obvious units. In fact, evolution is about a slow transition in an overall population. What qualifies as “chicken” (ignoring the many diverse modern types of chicken) involves a wide range of genetic traits (alleles) that are not encompassed in a single individual and continue to be modified from generation to generation.

The transition from non-chicken to chicken is a grey area in which several generations are involved, and therefore which includes many many chicken-and-egg events, with no one step representing the whole. Since the result of the process is an incomplete transition into various new characteristics rather than one single blueprint, a new species, "chicken", is only identified in hindsight when the species can be obviously identified as different from its ancestral stock.

Possibly, if life originated from an ooze or protozoa of some type, at first there may only have been cellular life that used division as a reproductive method but as multicellular creatures evolved, mutation led to sexes differentiating. Division of the reproductive task into sexual roles took the form of an ovum / fertilization sequence. The egg was therefore present at the same time as the creature that gestated/layed it, speciation into birds or turtles happens much later with such a scenario.

Well there you go.

And if you like going back in time, there is one thing that might amaze you: all human beings on this planet share a common ancestor: a woman born in Africa 200,000 years ago!

We know this from something called mtDNA.

Basically, every human gets their DNA from both their parents. But outside the cell is something called mtDNA. And you only get this from your mother. This means that all of the mtDNA in the cells of a person's body are copies of his or her mother's mtDNA, and all of the mother's mtDNA is a copy of HER mother's, and so on. Thus, no matter how far back you go, mtDNA is always inherited ONLY from the mother.

And so by following the chain the scientists can see that we all come from the same mother! The aborigine from Australia, the banker in New York, the sheik from Saudi. Not sure what the racists would make of that but personally I find it very reassuring.

And if you go further back – i.e. to your (our) 250,000 great grandparent – then you (we) arrive at a creature which all humans AND chimpanzees are directly descended.

Quite what OUR 250,000 descendent will look like is anyone’s guess of course. Probably be 10 feet tall, with a huge head and green skin I reckon!

Now where’s my spicy chicken wings?