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  • Writer's pictureDale DeBakcsy

How Fossils Get That Way: Paleontologist Anna “Kay” Behrensmeyer’s Years Amidst Rock and Bone.

When it comes to bones, immortality is far from a sure thing. We generally think that the road from bone to fossil is a straight-forward and all but assured one: Thing dies, stuff eats the soft tissue, the remaining bone gets buried and mineralized over time, and voila, fossil. In reality, the path to fossilhood is fraught with peril for a bone trying to make its mark on the historical record, and depends on a plethora of biotic and abiotic factors all conspiring against it. The particular branch of paleontology that studies the factors behind fossil formation is known as taphonomy, and among its luminaries few shine as bright as Anna “Kay” Behrensmeyer, who for half a century now has been researching what the fate of modern day bones might tell us about how to better interpret the fossil record bequeathed us by humanity’s deep past.


As an undergraduate at Washington University in St. Louis, Behrensmeyer had initially decided upon an art major, but was drawn towards geology and paleontology because of the questions it asked, the puzzles it posed, and the places it takes one. She was pulled particularly to the field of taphonomy after a field project in Wyoming where marine and land animal remains were found at the same site. This brought up the question of how faithfully we can construct the past on the remnants still existing today, and the challenge of finding better ways to analyze those remnants to say meaningful things about past organisms who for one reason or another didn’t make it into the fossil record.


That, however, was all in the future. In 1969, as a graduate student, she was invited along by Richard Leakey (who was also instrumental in providing early research opportunities in the careers of Jade Goodall, Birute Galdikas, and Dian Fossey) to serve as a geologist at his Koobi Fora digsite in Kenya. Here, Behrensmeyer discovered a collection of stone tools in a formation of volcanic ash known as a “tuff” which is today known as the KBS or Kay Behrensmeyer Site tuff. Radiometric dating seemed to indicate the tools were some 2.5 million years old, about 600,000 years more ancient than the remains famously found by Mary and Richard Leakey at Olduvai Gorge a decade earlier.



It was a momentous discovery for somebody who had not yet earned her PhD, and one which placed her at the center of an anthropological debate which ultimately settled on a date for the tools closer to those of Olduvai. Behrensmeyer, rather than becoming bogged down by that debate, continued on in her career, earning her PhD in 1973 in sedimentology and vertebrate paleontology for her work showing how different sedimentary environments altered the ultimate composition of fossils, allowing us to use the mineral composition of fossils to infer geologic facts about the ancient environments in which they were produced.


In 1981, Behrensmeyer began her work with the institution which has been her home for the past four decades, the Smithsonian. Here, she has worn a number of administrative and research hats that beggar belief, including acting as the curator for the National Museum of Natural History’s vertebrate paleontology department, conducting research for the Human Origins Program, and directing a multi-decade taphonomy project at Amboseli National Park in Kenya.


The Amboseli project is, briefly put, entirely rad. In it, Behrensmeyer employs analysis of current bone remains to determine what it takes for bones to enter the fossil record, and what connections there are between the bones that survive, how they survive, and the ecology of the region they belong to. She has determined that fossilization often occurs much more rapidly than we had previously believed, and furthermore, that unless bones get buried relatively quickly, i.e. within a few decades of the demise of their former owners, their chances of entering the fossil record are decidedly slim. Furthermore, the number and quality of bones available for fossilization can take dramatic turns based on regular relatively short term fluctuations in the relative abundance of different predators in an ecosystem. At Amboseli, the shift from a lion-dominant to hyena-dominant predator profile has meant a subsequent seventy-five percent decline in the amount of bones available for fossilization due to the more thorough scavenging practices of hyena herds.



While Amboseli is annually giving us new information (and has been doing so since 1975) about how bones become fossils, and what their abundance and wear can tell us about the worlds they came from, Behrensmeyer’s work with the Human Origins Program has built for us a picture of the slow progression of humanity that has substantially revised the “creative explosion” model which had dominated anthropological thought previously. Instead of holding that the main attributes of modern humanity - our capacities for tool-making, interactive large scale social associations, and symbolic thought - are the result of a sudden cognitive explosion that took place some 60,000 years ago, the Human Origins Program has revealed examples of complex social networks, sophisticated tool formation, and symbolic activity stretching back approximately 300,000 years, with elements of the modern Homo sapiens bag of tricks in evidence as much as 600,000 years ago.


It is easy to be blinded by the size of these achievements, each foundational in the story of humanity coming to knowledge of itself and the past, but to do so would be to ignore the tremendous significance of her work as Curator of Vertebrate Paleontology at the Smithsonian. Our nation’s curators are some of our greatest unsung heroes, fighting battles against steadily dwindling funding to maintain our nation’s natural historical collections, designing exhibits and displays to share our evolving knowledge of the Earth’s past with the general public, and carrying out fundamental research that pushes that knowledge forward. It is a massive job encompassing a dizzying number of administrative, scientific, and public relations skill sets, involving profound investments in time and energy for little personal glory, and those who elect to follow that path deserve all the reverent thanks we as a society can muster.


Behrensmeyer’s work at the Smithsonian for the past forty five years has brought the public a greater knowledge of its evolutionary past, and preserved the work of the paleontological community against the steady contraction of collection preservation funding that has rocked it over the past few decades. She has literally protected our deep past for us in the face of our own institutional inertia, and for that feat alone she deserves our gratitude, as do so many other museum curators working in virtual anonymity to keep the wheels of paleontology rolling forwards.


The stories that bones may tell, the artifacts of our long Homo sapiens past, the preservation of that past for the benefit of our future - the sweep of Behrensmeyer’s career is one that seemingly defies conventional boundaries of space and time, and with any luck she and those she has inspired will continue the path begun half a century ago for decades to come.


FURTHER READING:


I came across Behrensmeyer’s remarkable career in the pages of Roy Plotnick’s recent book about modern paleontology, Explorers of Deep Time (2022) which also features a plethora of other women doing awesome work in geology and paleontology. It’s an engaging and fun read I unreservedly recommend. If you want to learn more about the Human Origins Program, you can check out their website and then head over to Behrensmeyer’s Smithsonian webpage.

for links to her extensive publications!


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