IT’S EARLY OCTOBER 2017, A roasting-hot midmorning, and we’ve just left Tucson, Arizona, for the 80-mile drive to Murray Springs, a very rich and complex Clovis site about 14 miles southwest of the town of Tombstone and 20 miles north of the Mexican border. Our route takes us via I-10 and AZ-90 through increasingly sere scrub and semidesert under a merciless sky, but when we arrive at Murray Springs itself, park, say hello to the rangers at the gate, and walk the couple of miles of the trail around the archaeological site we find ourselves in a sort of oasis with abundant mesquite growing tall enough along the edges of a sinuous arroyo—a flood channel—to offer some welcome shade. Although flash floods still rip through here from time to time it’s rumored that the present lush environment owes more to treated sewage being dumped in the area.
Santha and I are accompanied by geophysicist Allen West and his wife, Nancy. Working with Jim Kennett, an earth scientist and oceanographer at the University of California, and Richard Firestone, a nuclear analytical chemist at Lawrence Berkeley National Laboratory, West is one of the principal investigators in a loose alliance of more than sixty scientists from many different fields who have joined forces since 2007 to try to solve a profound mystery. It concerns the Younger Dryas, the interlude of cataclysmic global climate change coinciding with the Late Pleistocene Extinction Event in which thirty-five genera of North American megafauna (with each genus consisting of several species) were wiped out around 12,800 years ago. Sharing their fate were the Clovis people and their distinctive culture with its characteristic “fluted-point” weaponry.
We climb down to the floor of the arroyo, which is about 2 meters deep and 12 meters wide at this point, and begin to walk along it. After a few moments Allen stops. “It’s around here that they excavated Eloise,” he says. He’s referring to one of the mammoths ambushed and butchered at Murray Springs by the Clovis people some 12,800 years ago. He describes how Eloise’s skeleton was found intact except for the hind legs, which had been chopped off right after she was killed. One was moved up and placed alongside her head. Archaeologists found the other a few hundred meters away, close to the residue of an ancient campfire. Part of a broken Clovis point was also found by the campfire, while the rest of it was “in Eloise.”
The archaeologist who excavated the mammoth in the 1960s, and who would bring Allen West and Richard Firestone to the site many years later, was Vance Haynes, Regents Professor Emeritus at the University of Arizona and a senior member of the National Academy of Sciences. The reader will recall that his adamant defense of “Clovis First” was a significant factor in extending the life of that now thoroughly discredited theory and in inhibiting other research indicating a much earlier peopling of the Americas.
As the discoverer and principal excavator of Murray Springs, however, Haynes deserves credit for drawing attention to a very curious aspect of the site—a distinct dark layer of soil draped “like shrink-wrap,” as Allen West puts it, over the top of the Clovis remains and of the extinct megafauna— including Eloise.
Haynes has identified this “black mat” (his term) not only at Murray Springs but at dozens of other sites across North America,1 and was the first to acknowledge its clear and obvious association with the Late Pleistocene Extinction Event. He speaks of the “remarkable circumstances” surrounding the event, the abrupt die-off on a continental scale of all large mammals “immediately before deposition of the … black mat,” and the total absence thereafter of “mammoth, mastodon, horse, camel, dire wolf, American lion, tapir and other [megafauna], as well as Clovis people.”
Haynes notes also that “The basal black mat contact marks a major climate change from the warm dry climate of the terminal Allerød to the glacially cold Younger Dryas.”
From roughly 18,000 years ago, and for several thousand years thereafter, global temperatures had been slowly but steadily rising and the ice sheets melting. Our ancestors would have had reason to hope that earth’s long winter was at last coming to an end and that a new era of congenial climate beckoned. This process of warming became particularly pronounced after about 14,500 years ago. Then suddenly, around 12,800 years ago, the direction of climate change reversed and the world turned dramatically, instantly cold—as cold as it had been at the peak of the Ice Age many thousands of years earlier. This deep freeze—the mysterious epoch now known as the Younger Dryas—lasted for approximately 1,200 years until 11,600 years ago, at which point the climate flipped again, global temperatures shot up rapidly, the remnant ice sheets melted and collapsed into the oceans, and the world became as warm as it is today.
. . . I ask Allen to explain the black mat to me. “I understand that the lowest part of it is full of impact proxies laid down at the time the mat began to form but clearly they’re not the mat itself.”
“The black mat formed on top of the layer of proxies,” Allen replies. “Down here it has a lot of charcoal in it. But it also has algal remains so it’s not just fire. The Younger Dryas changed the climate and made the area much wetter. Algae began to grow along the edges of the lakes.” He puts a hand on the black stripe along the arroyo wall: “So the remains of about 1,000 years of dead algae, charcoal, and a lot of other stuff are all embedded in here, and at the bottom of it, where the impact happened, we find iridium, platinum, and a layer of melted spherules where the temperatures must have been so high that they would have melted a modern car into a pool of metal.”
. . . “[W]hat we can be certain of was that this moment marked the end of their story, and the end of an epoch, really. There’s not a single Clovis point found anywhere in North America that’s above that black mat. They’re all in it or below it. And there’s not a single mammoth skeleton anywhere in North America that’s above it. A huge part of the die-off could have been as a direct result of the impacts themselves, but impacts and airbursts south of the ice cap, particularly as far south as New Mexico, would also have set off wildfires. There’s overwhelming evidence that gigantic wildfires raged at the onset of the Younger Dryas—in fact, more soot has been found at the Younger Dryas Boundary than at the Cretaceous-Paleogene Boundary. We did the calculations and it looks like as much as 25 percent of the edible biomass and around 9 percent of the total biomass of the planet was on fire and destroyed within days or weeks of the YDB. So in many areas if the animals weren’t killed outright they wouldn’t have been able to forage enough food afterwards to survive. The grass would have burned up, leaves on trees were gone . . . And you know, the other thing is that when comet fragments come in they’re traveling incredibly fast and they literally punch a hole in the atmosphere. They actually push the air aside and they bring in that super cold from space, and when they explode in the air that cold plume continues to the ground and you literally have things frozen in place if they were close enough to where the plume came down. It’s possible they were fried and then frozen all within a matter of seconds.”
