'Human Footprint' on PBS Terra describes 'The Mysterious Mass Extinction Hidden in LA'

Today's "evergreen educational entry" begins with PBS Terra describing The Mysterious Mass Extinction Hidden in LA, an excerpt from Human Footprint.

Beneath the streets of Los Angeles lies one of the most prolific fossil sites in the world. At the La Brea Tar Pits, millions of fossils including giant sloths, dire wolves, saber-toothed cats, and mammoths have surfaced from ancient asphalt, offering a rare glimpse into a vanished world.

In this episode of Human Footprint, Shane Campbell-Staton joins paleontologist Emily Lindsey to investigate the sudden disappearance of North America’s megafauna around 13,000 years ago. Together, they follow the trail of ancient life through radiocarbon dating, fossil excavations, and lake-bottom sediment cores.

For decades, scientists debated whether climate change or human hunters were to blame. But new evidence points to a more complex and unsettling cause: a dangerous combination of warming temperatures, ecological disruption, and the spread of fires… ignited by us.

This isn’t just a story about extinction. It’s a glimpse of how past crises mirror the present, and a warning about where we could be headed next.

I first mentioned that I was a paleontologist at the Tar Pits in Infidel 753 and I talk fossils. I explored my experience again in Kunstler, K-Dog, and I discuss prehistoric mammals for Darwin Day plus paczki on Fat Tuesday, PBS Eons explains 'How Plate Tectonics Transformed Los Angeles', and PBS Digital's Be Smart debunks 'The Biggest Myth About Climate Change', which is the most relevant to this video. There, I wrote "I have mentioned several times that I'm a paleontologist who studies Pleistocene fossils, particularly snails. What I don't mention is that I used data from the snails, clams, and plants of Rancho La Brea to reconstruct the late Pleistocene climate of southern California, so I'm quite familiar with natural climate change." I felt that was important enough that I recycled it in PBS NewsHour reports 'Record-breaking global temperature, raging wildfires highlight effects of climate change' plus Thursday broke another record and PBS Terra explains 'The REAL STORY of Climate Skeptics New Favorite Graph'. That gives me an expert perspective on the findings that the fire regime changed about 13,200 years ago, resulting in a changed ecosystem with humans but lacking the Pleistocene predators whose last fossils Emily Lindsey displayed for the camera.

When I was doing my research at the Tar Pits 40 years ago, I became quite familiar with the competing hypotheses of climate change and human overhunting (Paul Martin's overkill hypothesis) causing the terminal Pleistocene extinctions of New World megafauna. However, I also realized that overkill didn't replicate perfectly around the world. Humans arrived earlier in Australia than in the Americas, but it took thousands of years for the Australian megafauna to go extinct. The same was true in northern Eurasia, which had other humans, the Neanderthals and Denisovans, already living there for hundreds of thousands of years before modern humans arrived. And, of course, where the megafauna had co-evolved with human ancestors in Africa and southern Asia, most of the large animals survived into the present. I resolved these data by synthesizing them; late Pleistocene extinctions happened during the first episodes of major climate change after modern humans were first present. The mechanism I had in mind was that climate change stressed the populations of megafauna, which then couldn't withstand human hunting. That ancient humans could make the effects of climate change worse never occurred to me. As Shane Campbell-Staton said, "That is a plot twist I wasn't expecting."

Just because I wasn't expecting it either doesn't mean I don't accept it. I do. After all, I've been watching the fire season expand in California over the past 15 years. I even ask my students two questions about in the worksheet for Chasing Ice: "1. Chasing Ice opens with a montage of natural disasters. Name three of them." One of them is a wildfire. "How many months has the fire season increased in the American southwest since the 1980s?" The answer is two months, although last year's California fire season extended about four months into January, which I recounted in PBS Terra tells 'The REAL Story of the LA Fires | Full Documentary' for Flashback Friday. As Campbell-Staton said, this is uncomfortably familiar.

It also reminds me of two examples of why studying the past is important for understanding the present and predicting the future. The first comes from Prehistoric lions of Eurasia and North America for World Lion Day 2022: "one of the points of paleontology is to learn from the past and apply the knowledge gained to the present." The other I wrote in NOVA warns of 'The Next Pompeii' for the Ides of March.

[P]rocesses that happened in the past are likely to repeat in the future, so understanding the past is essential for preparation. This is a key takeaway from uniformitarianism, the concept that everything we see in nature is the result of everyday processes occurring over sufficient time, which is boiled down to "the present is the key to the past." It also means that the past is the key to the future.

File all the above under "it's a always a good day when I learn something new."

I also felt a lot of nostalgia seeing where I spent much of four years, but this entry has gone on long enough. Time to wrap it up. Stay tuned for another entry about the Creative Arts Emmy Awards.