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Toonsi Crater Speculation

Be patient with me while I talk about this.

(Picture from here.)

Humans separated from chimpanzees between 4-7 million years ago. This time is a significant point of discussion in the human evolution community. The most recent value I’ve found is 6.9-9 million years ago. (Original article here.)

Fossil timing is a bit different. The earliest genus associated with human evolution is Australopithecus. The ancestor of Australopithecus is Ardipithecus. The earliest known Ardipithecus is Ardipithecus kadabba. Ar. kadabba is thought to be 5.77-5.54 million years old. (See the above illustration to show the timeline I’m trying to describe.) Ar. kadabba is thought to be close to the dividing point between chimps and humans. Although, if the 6.9-9 million figure is borne out, there is a lost 2 or so million years to account for.

Somewhere between Ar. kadabba and Homo habilis, the populations changed from pre-human to human—maybe not modern human but for better or worse, everything in genus Homo is human.

There have been massive studies and speculation as to what caused that transformation. This has included pocket population isolation, changes in ecology, and specific mutations. But none of this is conclusive. There were ecological shifts in the areas where Ardipithecus, and subsequent Australopithecus, lived. Many of the Australopithecus species show specific adaptations to local conditions—which one would expect from evolution. As we know, correlation is not causation. We know a series of evolutionary events occurred but we’re hazy on the cause.

If we go back to the timing (see the above illustration again), we see Ar. kadabba a little less than six million years ago. This is followed by Ar. ramidus, around 4.4 mya. After that, speciation comes thick and fast until H. habilis shows up about 2.3 mya.

Ar. kadabba was discovered in the Middle Awash of Ethiopia. Ar. ramidus was discovered nearby in the Afar region. Australopithecus species existed in eastern Africa beginning in 4.2 mya and became widespread throughout eastern and southern Africa.

That’s the picture I want to paint: Ardipithecus living in Ethiopia, then Australopithecus a couple of million years later. Australopithecus spread around and eventually birthed Homo habilis.

My wife and I regularly watch geology YouTube channels. One of our favorites (and a favoritism we share with many) is GeologyHub.

A few days ago, we watched one of the new videos describing a new crater discovered in Saudi Arabia: Toonsi Crater, described in the original paper by Abdulrahman Toonsi. This crater borders the Harrat Rahat volcano formation. Toonsi’s paper suggests that the crater is quite old since there is no basalt of the volcano formation in the breccia created in the impact. The geologist behind GeologyHub believes it is considerably younger than that since the rims of the crater interrupt the basalt of the volcano field. He estimates it is 4-6 mya. GeologyHub estimates that the immediate fire zone of the impact to be about 320 miles away from the crater.

I’m listening to this and the dates stick out at me. I look up the material I described previously. Sure enough, the GeologyHub date happens smack in the beginning of the Ardipithecus/Australopithecus period. The crater itself is about five hundred miles from the Middle Awash and the Afar region of Ethiopia—out of the fire zone but well within any potential ecological disruption.

I am not saying that the Toonsi impact caused world wide ecological devastation like the Chicxulub impact did. I am saying there’s a potential impact event possibly dated to the cusp of some big changes in human evolution. Correlation is not causation but isn’t it interesting?

The research has not been peer reviewed so it could fall apart. I’m not sure it’s going to be—Toonsi is a 15 year old geologist of serious talent but that may not get him as far as he would like.

But I want somebody out there to look at it.

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