When the volcano blows

Nobel Prize-winning physicist Richard Feynman once said, "I would rather have questions that cannot be answered than answers that cannot be questioned."

The strength of science is in its ability to self-correct, but this does engender a problem; it may well be that some of the questions we're asking will never be satisfactorily answered.  There are sometimes when we must admit ignorance, and hold our determination to have everything figured out in abeyance -- possibly indefinitely.

That may be the situation we're in with regards to an interesting question surrounding the largest volcanic eruption in modern times, the eruption of Toba in the Indonesian archipelago.  This eruption dwarfed Mount Saint Helens, the 1883 eruption of Krakatoa, and even the catastrophic eruption of Tambora (also in Indonesia) in 1815, that threw so much in the way of debris up into the atmosphere that it caused the "Year Without a Summer," in which Quebec City got a foot of snow -- in mid-July.

The Toba eruption, 74,000 years ago, was bigger than all of the above; by some estimates, it threw a hundred times more in the way of pulverized rock into the air than Tambora did.  It is certain that it caused not only localized devastation, but worldwide climate change.  And the conventional wisdom is that it nearly wiped out the human species -- that we were driven into a genetic bottleneck, in which only a few survivors became the ancestors of everyone currently alive today.

The Toba caldera [image courtesy of the Wikimedia Commons]

Michael Rampino and Stanley Ambrose, of New York University, were amongst the first proponents of the Toba bottleneck theory.  In their paper "Volcanic Winter in the Garden of Eden: The Toba Supereruption and the Late Pleistocene Human Population Crash," published in 2000 in the Papers of the Geological Society of America, they write:

Genetic studies indicate that sometime prior to ca. 60,000 yr ago humans suffered a severe population bottleneck (possibly only 3,000-10,000 individuals), followed eventually by rapid population increase, technological innovations, and migrations.  The climatic effects of the paroxysmal Toba eruption could have caused the bottleneck, and the event might have been a catalyst for the technological innovations and migrations that followed.  The present results as to the predicted environmental and ecological effects of the eruption lend support to a possible connection between the Toba event and the human population bottleneck, and suggest that similar bottlenecks among other organisms might be expected at about the same time. 

However, it appears that the question is far from settled.  A paper by Eugene Smith et al. that came out last week in Nature, "Humans Thrived in South Africa Through the Toba Eruption about 74,000 Years Ago," completely counters the conventional wisdom -- and suggests that if the bottleneck did occur, it may not have been the fault of the volcano:

Approximately 74 thousand years ago (ka), the Toba caldera erupted in Sumatra.  Since the magnitude of this eruption was first established, its effects on climate, environment and humans have been debated.  Here we describe the discovery of microscopic glass shards characteristic of the Youngest Toba Tuff—ashfall from the Toba eruption—in two archaeological sites on the south coast of South Africa, a region in which there is evidence for early human behavioural complexity.  An independently derived dating model supports a date of approximately 74 ka for the sediments containing the Youngest Toba Tuff glass shards.  By defining the input of shards at both sites, which are located nine kilometres apart, we are able to establish a close temporal correlation between them.  Our high-resolution excavation and sampling technique enable exact comparisons between the input of Youngest Toba Tuff glass shards and the evidence for human occupation.  Humans in this region thrived through the Toba event and the ensuing full glacial conditions, perhaps as a combined result of the uniquely rich resource base of the region and fully evolved modern human adaptation.

The reason I bring this up -- besides the fact that I'm interested in human population genetics, and it's cool -- is that this may be a question that we simply don't have the data to answer.  It's possible that the "thriving" population that Smith et al. found was a localized group of lucky people, and elsewhere, humanity got clobbered.  On the other hand, it could be that the Rampino and Ambrose paper was simply wrong -- that the population genetics studies, which are not without their a priori assumptions, overestimated the extent of the Toba bottleneck (or the whatever-caused-it bottleneck).

But -- and this is the most critical point -- you keep looking.  If there's no definitive solution, you are forced to admit it, but the research doesn't stop there.  Ignorance is the beginning, not the end, of the scientific process.

So we may never know exactly how close humanity came to extinction 74,000 years ago.  The important thing is that we've asked the question -- and that science gives us a means to evaluate the evidence, and determine if a particular answer is supported.  And what we learn along the way will open up further avenues for exploration, enough to keep the scientific world occupied for a long, long time.

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Accidentally correct

One of the most wonderful moments in Douglas Adams's The Hitchhiker's Guide to the Galaxy occurs when Ford Prefect and Arthur Dent fire up the Infinite Improbability Drive, which allows a spaceship to pass through all points in space simultaneously.  Unfortunately, it has as a side effect altering the likelihood of every event in the vicinity of the ship.  As their ship is being zipped along, Arthur comes in with an alarmed look on his face.

"'Ford!' he said, 'there's an infinite number of monkeys outside who want to talk to us about this script for Hamlet they've worked out.'"

It's a standard way to explain the likelihood of extremely unlikely occurrences over long periods of time -- that something that exists at a very low probability (like monkeys randomly pounding keys on a typewriter and writing out the script to Hamlet) will eventually happen if you wait long enough.  It's like the random motion ("Brownian motion") of molecules, due to their thermal energy.  It's possible that all of them will, by chance, move in the same direction at the same time, and your cup of coffee will jump up off the table.  But as my long-ago thermodynamics professor said, "It is, however, extremely unlikely."

This all comes up because something that was incredibly unlikely just happened a couple of days ago.  Fasten your seatbelts and hold down your coffee cups:

Ken Ham said something that was scientifically correct.

Okay, he said it for the wrong reason, but he still was right, which kind of blew me away.  He was being asked about racism, and not only did he give the right general response ("racism bad") he said, "The answer to racism is believing the true history of humans in Genesis (as confirmed by science): we're all one race — not different races.  When politicians and media talk about 'races' of humans, they are actually fueling racism there's only one race, the human race...  There are no truly black or white people — all are basically brown (pigment melanin) — but differing shades because of genetic variability."

Which, if you leave out the "true history in Genesis as confirmed by science" part, is actually pretty much correct.  The things we lump together as "race" -- physical features such as skin color, eye color, hair color and texture, and so on -- are actually not very good indicators of degree of relatedness between different human ethnic groups.  Geneticist Richard Lewontin writes:

It is clear that our perception of relatively large differences between human races and subgroups, as compared to the variation within these groups, is indeed a biased perception and that, based on randomly chosen genetic differences, human races and populations are remarkably similar to each other, with the largest part by far of human variation being accounted for by the differences between individuals... 

Since such racial classification is now seen to be of virtually no genetic or taxonomic significance... no justification can be offered for its continuance.

Now, to be sure, race and ethnicity have a great deal of cultural significance.  But its biological significance is nil.  As my college genetics professor, Dr. Lemmon, put it, "There is more human genetic variability in one hundred-square-mile area of Tanzania than there is between a typical Englishman and a typical Japanese man."

Which makes sense, of course, given that East Africa is where the human race evolved.  It's unsurprising that we still see tremendous diversity there.  Add that to the suggestion (well supported by evidence) that Homo sapiens went through a major genetic bottleneck about 74,000 years ago -- some researchers believe that the survivors may have numbered less than 2,000 individuals -- and a lot of the diversity (and lack thereof) has a fairly natural explanation.

[image courtesy of the Wikimedia Commons]

It also makes claims about racial superiority/inferiority seem kind of idiotic, doesn't it?

So Ham is right, although for entirely wrong reasons.  He's correct that traits such as skin color are very variable; but the idea that the genetic variability just kinda happened is ridiculous.  There's a big difference in selective pressure on the genes that control melanin production if you live in (for example) Kenya as compared to living in northern Finland.  In Kenya, the main driver is protecting the skin from harsh sunlight, and thus higher melanin production; in Finland, it's UV-mediated vitamin D synthesis, and thus lower melanin production.

In other words, natural selection and evolution.

Anyhow, I found it remarkably like Adams's infinite monkeys when I read Ham's statement, given that most of the rest of what he believes has no scientific basis whatsoever, even on the level of general gist.  But, to look at it a different way: as my dad used to say, even a stopped clock is right twice a day.