Tuesday, 5 April 2005

Hobbits, SuperVolcanoes, and Space Travel

I've blogged before about all three topics, Hobbits, SuperVolcanoes, and Space Travel. Now for a post which combines all three - and with important relevance to the foreseeable future.

From The Australian :
As if earthquake-ravaged Indonesia doesn't have enough to worry about, now scientists warn that a Sumatran super-volcano might blow its top at any time.

If it does, the blast will toss hundreds of thousands of cubic kilometres of rock and ash into the atmosphere, dwarfing the eruptions of Krakatoa, Mount St Helens, Pinatubo and any conventional volcanic explosion of the past tens of thousands of years.

"These super-volcanoes are potentially the greatest hazard on Earth, the only greater threat being an asteroid impact from space," said Ray Cas, a vulcanologist with Monash University in Melbourne.

Professor Cas said a "major tectonic event" could be enough to trigger a deadly super-volcanic eruption.

The likelihood that the Toba – the largest super-volcano on Earth – will erupt has increased significantly due to geological stresses generated by the recent quakes.
Worse, Toba sits directly atop the faultline running down the spine of Sumatra. That is where seismologists say a third quake might strike.
And here's what we think happened last time Toba blew. But first, a remark about a most remarkable mammal - us.
Human beings in civilizations that think about such things, pride themselves on their (occasionally) towering intelligence, their scientific, technological, philosophical, economic and artistic accomplishments. Scientific nomenclature knows humans as Homo sapiens ("wise man"), nicely reflecting such high self-esteem.

Leaving the towering but hard-to-measure intelligence aside, there are other, much more easily measured if rather less well-publicised aspects of Homo sapiens that set off the species quite spectacularly from other life forms:

Of all living things on earth weighing more than a few grams/ounces or measuring more than a few cm/inches,

(a) Homo sapiens is today the only truly world-wide species, living as it does in flat and rugged, in hot and cold, in dry and wet places, and practically everywhere in between. The species has even gained a recent foothold in Antarctica, and in large cities it has created its very own environment.

(b) Homo sapiens has by far the largest numbers of individuals (estimated 6,300,000,000 in 2003)

(c) Local variations (known as "races") also show extraordinarily low levels of within-and between-population genetic variation in comparison to the apes. This also supports an extremely recent origin for Homo sapiens (ref. Ferris et al., 1981; Ruvolo et al., 1993). Only around 10% of the limited human genetic variation is accounted for by differences between populations (ref. Lewontin, 1972; Relethford, 1995).

(d) Homo sapiens has very little genetic diversity despite its huge numbers.

The last point is the oddest - and the least widely known. It is also one of the arguments in favour of a relatively recent bottleneck rather than one much longer ago (e.g. one proposed for 2 million years ago by the "regional continuity" supporters, ref. Hawks, et al, 2000). The low genetic diversity implies that the present teeming multitudes of human beings goes back to a small and relatively recent founding population.

Genetics has this to say on Homo sapiens:
... we have sequenced 10 kb of non-coding DNA in a region of low recombination at Xq13.3 from 70 humans representing all major language groups of the world. In addition, the same sequence has been determined from 30 chimpanzees, representing all major subspecies, as well as bonobos. Comparison to humans reveals an almost four-fold higher diversity and a three-fold greater age of the most recent common ancestor of the chimpanzee sequences. Phylogenetic analyses show the sequences from the different chimpanzee subspecies to be intermixed ... These data, as well as preliminary work in the other great apes, indicate that the human genome is unique in carrying extremely little nucleotide diversity. (ref. Kaessman H. et al, 2000)
Note the "e.g. Toba" bit. It's important. To continue:
Estimating how low the number of members of the species Homo sapiens could have been to account for today's uniformity involves a number of variables that are anything but clear-cut. It has been estimated that only 40-600 females (which translates into a total population of less than 3,000 persons; Harpending H.C. et al. 1993) came through the bottleneck. Another estimate arrived at 500-3,000 females (ref. Rogers A.R. 1993) and yet another at 1,000 to 4,300 individuals (Ayala F.J. 1996; Takahata N. at al. 1995). The highest estimate so far has 10,000 females of reproductive age as the minimum (ref. Ambrose S.H.. 1998). Even if the highest estimate is accepted, we are talking about the entire human race numbering no more than the population of a small country town today.

Such a small group could not have been widespread but had to live (and survive Toba) in a relatively small area...
Again, and survive Toba. Because when it blew, it dramatically cooled World Climate.
For a long time it was thought that of all the the hominid groups, only Homo sapiens and Homo neanderthalensis had come through the bottleneck. The last decade has shown that this was not so. At least two Homo erectus species also made it, and more may await discovery.

In the following we have a look at each of the four groups that we know have come through:
  • Homo Neanderthalensis
  • Homo erectus (Ngandong 6)
  • Homo floresiensis
  • Homo sapiens
While the forward re-dating of a known Homo erectus species by more than 200,000 years to be contemporaneous with Homo sapiens was a sensation among the cognoscenti and specialists, the next major discovery was a headline shocker: in September 2003 a single (probably female) skeleton was discovered on the Indonesian island of Flores that belongs to an entirely new Homo erectus species: it was named Homo floresiensis. The species is tiny and has inevitably been nicknamed "the Hobbits".
We, being of the Andamanese Association and interested in the short-statured Asian Negrito people, of course thought that unknown groups of Negrito people could have survived in inaccessible island interiors. This is still a possibility, but perhaps reality will turn out even more outrageous, with non-human members of the genus Homo involved! Only a year ago such a thought would have been purest science fiction, but with the discovery of Homo floresiensis this is now a distinct if still somewhat unreal possibility.
Of the four species of the genus Homo that made it through the Toba bottleneck, only one is left today: Homo sapiens.

It was not the number of individuals that brought "victory" (if victory is what it is). It was an obsessive interest in technology.

What Homo sapiens is now doing is that he
  1. continues his fascination with technology,
  2. has begun to multiply to vast numbers, and
  3. tries to continue his expansion to the planets
And since this rock we're on is somewhat more exciting than we'd like, subject to Ice Ages, Super Volcanoes, the odd Dinosaur-Killer Meteorite etc, speaking as a member of the species in question, I think this is a Good Thing.

But until then, the best way to ride out a Toba eruption is to do so in a place a bit to the Eastward (upwind), and a bit to the southward (just the other side of the equator). India and Malaysia and much of the Middle East will get covered with 3-5 Metres(!) of Ash, the global temperature will plummet 5C or so, and the glaciers will come back to their old haunts of Europe and North America.

This could be a bit of a worry for us here in Australia. Because a lot of people will survive the immediate effects, and will be looking for a new place to set up. Assuming a crash program of coal-powered water desalinisation (global warming would be a desirable side-effect!), we may be able to increase the carrying capacity of the place to over 100 million. But that will take time, and our allocation might be over a billion.


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