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Rob Sheldon on the sixth great extinction

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Further to: Is there a sixth great extinction in progress? (It would help if a key exponent was anyone but Paul “Population Bomb” Ehrlich, a contender for the heavyweight champ of wrong-headed predictions), at Evolution News & Views, Rob Sheldon offers

While the criteria may sound quantitative, and the increase in extinction rate qualitatively higher, there is a missing factor in this calculation.

Dr Sheldon
Rob Sheldon

First, the extinction rate in the past is determined from fossils. Since almost by definition, fossil animals are nearly all extinct today, the extinction rate is close to 100 percent. But the key thing is that not all species are represented in the fossil record.

Second, the present extinction rate is determined from surveys of living organisms. This is going to bias the much smaller populations observed today, as well as bias the surveys that “haven’t seen a delta smelt in twenty years.”

The net result of these two considerations is that fossil extinction rates are smoothed over tens of millennia, whereas today’s extinction rates are spiky and represent maybe tens of decades at most. If we smoothed our present extinction rates over a few millennia, it would be amazing how much smaller the “rate” would be. In mathematical terms, dx/dt is scale dependent.

In addition, fossils represent such a small fraction of the living population that it is very difficult to infer an extinction rate from them. More.

See also: from Evolution News & Views Re Sixth Great, Here’ why no one trusts science reporting any more

A friend writes to say, “Sixth great extinction? Elizabeth Kolbert had an article on that in The New Yorker 6 years ago, May 2009.” Here:

Of the many species that have existed on earth—estimates run as high as fifty billion—more than ninety-nine per cent have disappeared. In the light of this, it is sometimes joked that all of life today amounts to little more than a rounding error.

A book, too of the name. And National Geographic asked two days ago, “Will Humans Survive the Sixth Great Extinction? Given that the Population Bomb failed to detonate, the strategy now seems to be, persuade people we’ll go down with the ship instead of crowd all other life forms off the planet.

Out of interest, if all of life today is just a rounding error, is there evidence that the biomass (the mass of all living vs. non-living creatures on the planet) is lower than it was in, say, the Cambrian? The Jurassic?

If not (and especially if it is actually higher), and assuming that evolution happens, how exactly are we to interpret such claims?

Or is it just same crock, different a-crockalypse?

I (O’Leary for News) wish they would go back to obsessing about Whole Foods.

See also: Vince Torley’s more reasonable figures. File in your Antidote to Hysterical Nonsense kit, along with: Do we have the right to eradicate species.

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