The Speculist

Addwaita the Tortoise was reportedly 250 years old when she finally died this past Wednesday. If that age is accurate, then she hatched in the year 1756. Here in the U.S., well... there was no U.S. But here in America the French-Indian war was in its second year. And Mozart was born that year in Austria.

Addwaita herself seems to have lived a rather interesting life for a tortoise.

[S]he was one of four tortoises brought to India by British sailors from the Seychelle islands as a gift for Lord Robert Clive of the East India Company. Clive was instrumental in establishing British colonial rule in India, before he returned to England in 1767.

While the other three tortoises died, Addwaita reportedly thrived, living in Clive's garden before being moved to the zoo [in 1875].

Addwaita is an example of nature experimenting with the limits of life span. While nature's at it, why not just grant immortality? It would seem to be an obvious gift. Reproduction is the sole goal of evolution. And if you're dead, you can't reproduce, right? On the other hand, I suppose that if you haven't hooked up at least a few times in 250 years, nature has a right to give up on you. Pandas, for example, seem to be testing nature's patience.

The reason nature hasn't produced any animals with unlimited life spans is because staying alive - for whatever length of time - is a heroic act of wrenching order from chaos. It takes energy and a healthy biological system. And all systems fail. You can build redundancies into a sytem to put off failure. Perhaps, as Kathy suggested, these tortoises have a different redundant system. But, ultimately, even the Addwaita's among us die. The redundancies fail too.

When it comes to life spans we humans are actually very fortunate. Life span among other animals tend to follow some basic rules.

1. Body size - the bigger the animal, the longer it lives.

2. Fecundity - the more offspring that an animal is capable of producing, the shorter it lives.

3. Brain size/body size ratio - the greater the ratio the longer the life.

Perhaps these rules aren't a complete explanation for human longevity. A while back a commenter suggested that we humans have another reason to live a long time - teaching and caring for the next generation. The fact that we have a complex language means that we can teach things that take years to explain - complex things.

Things like molecular biology.

We humans are, for now, the practical distinction between nature and evolution. Evolution doesn't "care" how long any individual creature lives - as long as enough members of the species live long enough to spawn the next generation. Senescence is the product of evolutionary neglect - a lack of evolutionary pressure to live longer - not part of some grand design to clear the way for future generations.

But through evolution nature produced a species that both cares about life span, and has the potential to do something about it. Senescence could not be eliminated with evolution alone. A couple more informational epochs had to come along.

But conquering senescence is only natural.