A physicist says his latest research may finally put to rest one of the most vexing theories about America’s natural history: that the giant fauna of the Ice Age — and the culture of humans who hunted them — were wiped out by a cosmic impact.
Studies of rock samples from the Channel Islands of California to the creeks of Oklahoma have failed to turn up any evidence, he says, that supports what’s known as the Younger Dryas Impact Hypothesis.
The missing evidence? Diamonds.
For a decade, the impact theory has posited that a period of sudden cooling that occurred around 12,900 years ago, known as the Younger Dryas event, was caused by a collision with Earth by a meteorite, comet, or some other celestial object.
Experts don’t dispute that Younger Dryas cold snap actually happened. The most widely held theory is that it was caused by rapid melting of glaciers at the end of the Ice Age, which inundated the northern oceans with fresh water and created a sudden change in ocean currents and, therefore, climate patterns.
But proponents of the impact theory argue that a celestial impact triggered widespread wildfires and blanketed the atmosphere in dust, causing a collapse of ecosystems that led to the demise of such iconic animals as the mammoth and the mastodon, as well as the decline of the widespread Clovis culture.
This, despite the lack of any obvious evidence of such a recent impact.
But supporters of the impact hypothesis have long argued that proof can be found at a microscopic scale, in the form of nano-sized diamond crystals, produced by the energy of the space crash.
Dr. Tyrone Daulton of Washington University in St. Louis describes the impact scenario as “diamonds rain[ing] from the sky as the woolly mammoths fell in their tracks across North America.”
But Daulton conducted a thorough analysis of samples that were found by other studies to have contained such diamonds.
“My goal was to identify nanodiamonds,” Daulton said in an interview, “that is, confirm their presence, if present, and study them, if present.
“I was unsuccessful. No diamonds were found.”
The impetus for his study, he said, was a one-page article in the journal Science published in 2009 by Dr. Douglas Kennett of the University of Oregon, which reported the presence of nanodiamonds in a layer of rock that supporters of the impact theory call the Younger Dryas Boundary — a stratum that dates to 12,900 years ago.
A reporter from Science, who was doing a write-up about the paper, contacted Daulton for comment, because Daulton was known for his study of formation of diamonds in space, such as during the formation of stars.
Daulton decided to do his own research to test the claims made in Kennett’s paper and others.
(See a strange find recently made on the same island: “‘Unusual’ Mammoth Fossil Discovered on California Island“)
“My coauthors have studied the Arlington Canyon site in great detail and have collected a large amount of data there,” Daulton said.
“My coauthors were able to locate the exact same outcrop section that Kennett et al., sampled for their studies.”
Daulton and his colleagues collected tiny spheres of carbon from the Arlington site, ground them up, and then inspected them using transmission electron microscopy.
“Despite my efforts, I was unable to locate any diamonds,” he said.
Daulton added that the most of the “nanodiamond” evidence reported by impact proponents is not true diamond but rather is said to be hypothetical phases of carbon, called “n-diamonds” or “i-carbon,” whose very existence is controversial.
“They are hypothetical phases,” he said.
Daulton said that his observations of the tiny spheres from Santa Rosa Island may explain why they may have been misidentified.
(See new insights into ancient human history on the island: “11,000-Year-Old Seafaring Indian Sites Discovered on California Island“)
Rather than being made of pure carbon, the spheres turned out to contain small amounts of copper compounds, which can create the same patterns of scattered light and electrons — known as diffraction patterns — that have been attributed to the hypothetical carbon structures.
“I found nanoparticles of copper and copper oxide that yielded diffraction data nearly
identical to that ascribed to controversial ‘n-diamond’ and ‘i-carbon’, respectively,” Daulton said.
“The presence of nanocrystals of copper is significant, because they can be easily confused with the controversial ‘n-diamond’, which represents the majority of the so-called nanodiamond evidence presented by the impact proponents.”
Daulton also pointed out that a similar analysis of purported nanodiamonds from Oklahoma returned similar results.
(See the latest finds from Oklahoma: “11,500-Year-Old Bison Butchering Site Discovered in Oklahoma“)
Daulton did not analyze those samples himself, but he summarized recent findings about them in his paper.
But soon after, when a graduate student analyzed the same samples, she found no traces of diamonds at all.
“We are not talking about a sample with a relatively marginal or small amount of nanodiamonds,” Daulton said.
“We are talking about a sample with the greatest reported concentration of nanodiamonds of all Younger Dryas Boundary sites.
“If that measurement cannot be reproduced, it draws into serious question the abundance
measurements performed at all other Younger Dryas Boundary sites.”
“The recent Bull Creek data is very revealing,” he added.
As a physicist whose work largely focuses on materials science and astronomy, Daulton has found himself drawn into one of the most heated debates in North American natural history.
“At one point, I had never heard of the Younger Dryas,” he said.
“I learned it was an interesting time marked by dramatic changes that prehistoric people experienced and lived through.”
(See the latest discovery from the Channel Islands: “Ancient Seafarers’ Tool Sites, Up to 12,000 Years Old, Discovered on California Island“)
But given the lack of reproducible results that he’s found, he and his colleagues remain unpersuaded by the Younger Dryas Impact Hypothesis.
“Studying science is very difficult, and they say, the devil is in the details,” he said.
“One needs to carefully examine the reported evidence and the methods used to collect that evidence, especially evidence used to support an extraordinary claim such as the Younger Dryas impact.”
Daulton’s research appears in the Journal of Quaternary Science.
Daulton, T., Amari, S., Scott, A., Hardiman, M., Pinter, N., & Anderson, R. (2017). Comprehensive analysis of nanodiamond evidence relating to the Younger Dryas Impact Hypothesis Journal of Quaternary Science, 32 (1), 7-34 DOI: 10.1002/jqs.2892
Kennett, D., Kennett, J., West, A., Mercer, C., Hee, S., Bement, L., Bunch, T., Sellers, M., & Wolbach, W. (2009). Nanodiamonds in the Younger Dryas Boundary Sediment Layer Science, 323 (5910), 94-94 DOI: 10.1126/science.1162819