Large Southeast Asian Meteor Impact Location From 790,000 Years Ago Found

The details of a meteor impact that caused global climate changes that may have been pivotal in hominin evolution are now known with much more specificity. 

[T]he impact point of a meteorite that struck the Earth approximately 790,000 years ago lies buried beneath a volcanic field in southern Laos. . . . .  

Prior research has shown that approximately 790,000 years ago, a large meteorite (the largest known young meteorite impact) struck Earth in the Eastern Hemisphere. So great was the impact that debris was strewn across a tenth of the entire planet's surface. Scientists know about the impact because of bits of glassy clasts known as tektites have been found in places like Antarctica, Australia and Southeast Asia. Prior evidence also suggested the impact site was likely somewhere in Southeast Asia, but until now, the exact location has been unknown. In this new effort, the researchers have found evidence that suggests the reason the crater has not been found is that it is hidden beneath a volcanic field—and they provide four lines of evidence to back up their claim. 

From here. The paper and its abstract are as follows:

Significance  

A field of black glassy blobs, strewn across about 20% of Earth’s Eastern Hemisphere, resulted from the impact of a large meteorite about 790,000 y ago. The large crater from which these tektites originated has eluded discovery for over a century, although evidence has long pointed to a location somewhere within Indochina, near the northern limit of the strewn field. We present stratigraphic, geochemical, geophysical, and geochronological evidence that the ∼15-km diameter crater lies buried beneath a large, young volcanic field in Southern Laos.  

Abstract 

The crater and proximal effects of the largest known young meteorite impact on Earth have eluded discovery for nearly a century. We present 4 lines of evidence that the 0.79-Ma impact crater of the Australasian tektites lies buried beneath lavas of a long-lived, 910-km3 volcanic field in Southern Laos: 1) Tektite geochemistry implies the presence of young, weathered basalts at the site at the time of the impact. 2) Geologic mapping and 40Ar-39Ar dates confirm that both pre- and postimpact basaltic lavas exist at the proposed impact site and that postimpact basalts wholly cover it. 3) A gravity anomaly there may also reflect the presence of a buried ∼17 × 13-km crater. 4) The nature of an outcrop of thick, crudely layered, bouldery sandstone and mudstone breccia 10–20 km from the center of the impact and fractured quartz grains within its boulder clasts support its being part of the proximal ejecta blanket.

Kerry Sieh et al., "Australasian impact crater buried under the Bolaven volcanic field, Southern Laos," Proceedings of the National Academy of Sciences (2019) (open access). DOI: 10.1073/pnas.1904368116 (Companion commentary from PNAS here).

Why Care?

This impact was the most notable climate event on Earth prior to the Holocene (i.e. the last 10,000 years) at a time the coincides with several key moments in hominin evolution.

The meteorite impact in question pre-dates the evolution of modern humans and either precedes or coincides with the evolution of our archaic hominin sister species Homo neanderthalensis, Homo denisova, and Homo heidelbergensis (possibly the direct evolutionary ancestor of modern humans and a mother species rather than a sister species, the exact relationship is unclear). It wouldn't be unreasonable to conjecture that the global climate impact that arose from this impact was a major factor that lead to the evolution of the shared predecessor of these two species. (I side with those who consider Neanderthals to be a separate species from modern humans in the same genus, rather than a subspecies of modern humans based on evidence of hybrid incompatibility between modern humans and Neanderthals when they admixed.)

It also is close in time to the earliest evidence of the archaic hominin Homo floresiensis (a.k.a. "hobbits") on the island of Flores in Indonesia. It wouldn't be an unreasonable conjecture that this impact was pivotal in the event that cause H. florensiensis to migrate to the island of Flores.

H. florensiensis, however, is probably much more basal in the hominin evolutionary tree even than Homo erectus (which evolved around 2 million years ago in Africa and had spread to Asia many hundreds of thousands of years before this meteorite impact).

It is also close in time to the earliest evidence of archaic hominin species in the Philippines, Homo luzonensis (whose existence was just confirmed in 2019 with bones from this species). It wouldn't be an unreasonable conjecture that this impact was pivotal in the event that cause H. luzonensis to migrate to the Philippines. Limited information makes classification of H. luzonensis in a hominin evolutionary tree difficult.