Lauren Schroeder is studying human evolution in a new way, thinking about more than just natural selection.
For a long time, scientists who study ancient humans have mainly looked at how they adapted to their environment.
Lauren Schroeder studies how humans have changed over time. She loves one fossil so much that she got a tattoo of it! It’s a skull of a Homo habilis, which is about 2 million years old.
Ever since she was 3 years old, Lauren Schroeder has been fascinated by dinosaurs. By the time she was 10, she was already intrigued by bones. In her second year of university, she began studying the early evolution of a group of ancient humans called the Homo genus. This interest became the focus of her Ph.D. Many fossils have amazed her over the years, but one that holds a very special place in her heart is the skull of a 2-million-year-old Homo habilis. She loves it so much that she got it tattooed on her forearm.
“I’m glad to say I’m doing what I’ve always wanted to do,” she says.
Schroeder, a scientist who studies ancient humans at the University of Toronto, tries to understand how humans have changed over time. One way is through natural selection, where changes help them fit better into their environment. But not all changes are because of this. Some happen randomly or aren’t needed. Even though there are these other ways, scientists have mostly focused on adaptation when looking at how ancient humans changed.
When Lauren Schroeder was studying for her Ph.D. at the University of Cape Town in South Africa, she wondered if scientists were focusing too much on natural selection to explain changes in ancient humans. “It seemed like there was something important we weren’t looking at,” she says. Not many studies had thought about how other things, like genetic drift and gene flow, might have played a role. “That was a big moment for me,” she says. “These are really big questions that nobody has asked yet. I want to try to find the answers.”
Since then, Lauren’s studies have shown that things like genetic drift and gene flow are more important in how humans have changed over time than we thought before.
“All of Lauren’s research has been really important for science,“ says Benjamin Auerbach, a scientist at the University of Tennessee, Knoxville. “Because of her work, we might talk about how people changed over time in a new way.”
The power of luck
Schroeder’s research is all about understanding how and why different body parts in humans (or other animals) developed. We call this “morphology.“
These are tricky questions to figure out because fossils usually don’t have DNA we can use. Scientists who study ancient humans look at the shapes of bones, use what we already know, and do lots of math to understand how humans changed over time. Lauren loves math, so she’s happy about that!
Before doing math, Schroeder looks closely at the features of fossils. For her Ph.D. work, she traveled to different places in Africa to scan and study ancient human skulls. These skulls were from a long time ago, some as old as 2.8 million years! She found that some features of the skulls, like the jaw, changed a lot. This probably happened because early humans had to adapt to new foods, which changed the shape of their jaws over time.
But here’s something interesting: when Schroeder studied the shapes of braincases in different ancient humans, she found something unexpected. She wrote about it in 2017 in the Journal of Human Evolution. It seems like genetic drift, a process where some genes disappear by chance, might have played a role. This means that the shape of their braincases changed just by luck!
Schroeder also studies animals that are alive today to learn more about how our ancestors evolved. Another thing she looks at is gene flow, which happens when genes move from one group of animals to another when they mate. This can happen when two different kinds of animals have babies together. Looking at fossils of these mixed animals could help us understand how they evolved. But right now, it’s hard to tell if a fossil is from a mixed animal or not.
Schroeder wants to make it easier by creating a plan using the shapes of animals that are alive today and are mixed together. She started with looking at the skulls of coyote-wolf mix animals (because she loves dogs!) and found some traits that are the same as other mixed animals. She wrote about this in 2021 in the Journal of Morphology.
Changing stories
Schroeder, who is from South Africa, noticed when she was in college that most of the research about ancient humans in her country was done by scientists from other countries. She found out that only a very small number of papers written about this topic by African scientists were published in a journal called the Journal of Human Evolution from 2016 to 2021. She wrote about this in the journal in January.
“Even though many studies about old humans are done in Africa, most of the scientists doing this work are white,” she says. As a Black African woman, “it felt really lonely there for a while.” Schroeder has had a hard time getting her research published, and she’s gotten unfair feedback on her work because of her gender. She’s also faced racism.
Some things have gotten better. When she went to conferences for scientists who study people and animals, she used to see only a few Black people. But when she went to one recently, there were a lot more. But we still have a lot more to do. She thanks her mentors for helping her in the beginning and a group called
Black in BioAnth Collective for trying to make things better in this field.
“It wasn’t easy for her to get to where she is, but she made it,” says Rebecca Ackermann, who helped Schroeder when she was studying for her Ph.D. at the University of Cape Town. “And now she can do whatever she wants.”
Schroeder recently got a permanent job at the
University of Toronto. She’s the first person in her family to go to college, so this is a really big deal for her and her parents. “My parents don’t always understand what I do,” she says, laughing. “But we’re all so happy and surprised that I’ve made it this far.”
