How did the paleoenvironment shape humans evolution?
Next Generation Science Standards:
Key Vocabulary: fossil, paleontologist, extinct, adaptations, species, traits, paleoenvironment, natural selection
Millions of years ago, Eastern Africa was home to a small group of species called hominids, the family of primates that includes gorillas, chimpanzees, orangutans, humans, and their ancestors. The descendants of these apes would go on to build supercomputers, split the atom, even walk on the Moon. For years researchers have wondered what the world of these early humans was like; how they lived and the conditions that led to their success. Denise Su, a paleoecologist with the Cleveland Museum of Natural History, has dedicated her work to answer these questions. Dr. Su’s research on the paleoenvironment of early humans has to lead to a greater understanding of the world of the earliest humans ancestors.
In a field site afar, far away…
Africa’s Eastern Rift Valley is home to some of the most stunning, if not desolate, landscapes on Earth. Here, tectonic forces are ripping the continent in two, exposing rocks millions of years old. It was in this region that in 1974, Don Johnson and his team, who at the time was also working for the Cleveland Museum of Natural History, found a 3.2 million-year-old fossil of a human ancestor. The nearly complete skeleton of Australopithecus afarensis has come to be known around the world as Lucy and was the first fossil evidence of our forebears walking upright.
Around 1500 miles to the south of Lucy’s discovery, is the Laetoli region of Northern Tanzania. It’s one of the most remote places on the planet and where Dr. Su’s fieldwork has taken her for the last 18 years. “We are camping in the middle of nowhere,” says Dr. Su. “This means that we take everything we need with us – tents, sleeping pads, petrol, food – which require a lot of planning beforehand.” With the closest town a 4-hour drive away, running out of basic supplies or getting sick or injured so far from a hospital means extra precautions need to be taken, as well as a good medical supply kit.
Why come to such an isolated and unforgiving place? Because it’s one of the best locations in the world to find fossils and artifacts from early hominids. Dr. Su and her team spend several weeks or months in the field at a time, looking for as much evidence as possible. “I look for anything and everything that will give me a piece of the puzzle,” says Dr. Su. Fossilized bones, plants, and pollen, as well as ancient soil and geological samples, are all important clues that help shape our understanding of what area was like for early hominids.
Once the fossils have been collected, they are brought back to the lab for analysis. Dr. Su and her team examine each specimen to understand the paleoenvironment, the environmental conditions of a particular time in the geologic past. How an animal ate or moved and what kind of plants were flourishing at the time help Dr. Su understand the ecological community of early hominids. “I take all of these data and put it together to try to understand what the paleoenvironment was like,” she says. “For example, if we find a lot of remains of animals that lived mostly in trees and very few animals that eat mostly grass, we can infer that the environment at the time was probably a dense forest.” By reconstructing the ecosystem at the time, Dr. Su can paint a picture of the ecological community in which our ancestors lived.
The Real Garden of Eden
So what was the world of the earliest humans really like? The truth is that there was no one type of environment in which hominids made their home. “Fossils of A. afarensis have been found in lots of different sites across Eastern Africa and each of these sites has slightly different habitats,” says Dr. Su. Some groups seemed to have preferred grassy savannas while other preferred dense woodlands and forests. Many of the sites where hominid fossils have been discovered were close to a large river or lake, giving our predecessors access to clean water.
Though the culture of our earliest ancestors cannot be preserved in the rock record, we do have some clues about their way of life. By looking at fossilized teeth and bones, we can get an idea of what hominids ate and where they lived. A.afarensis was able to survive by being a generalist; grasses, seeds, leaves, fruits, and nuts were all part of their diets. This gave them a big evolutionary advantage: by having a broad diet, early humans were able to eat whatever food was available to them. Without a supermarket around the corner, being a picky eater could leave you starving.
Reconstructing the environments of hominids is crucial to understanding how humans evolved, but questions still remain. How did hominids, who were without sharp teeth and couldn’t run very fast, flourish in the unforgiving conditions of the African savannas and jungles? What were the conditions that made walking upright an evolutionary advantage? And what were the selective pressures that favored humans to develop complex language, abstract thought, toolmaking, and other characteristics of higher intelligence? While we still have much to learn about the evolutionary rise of humanity, Dr. Su’s research has given scientists new insights of this ancient world and will continue to provide details on the story of our ancestors.
- Smithsonian Institution has a great interactive showing all species in the human family tree over the last 6 million years. Click on each species to learn about how they lived, what they looked like, and what fossils have been found.
- Science Friday has a segment with Dr. Su and how she uses fossilized plants, pollen, and bones to reconstruct these early environments and how they shaped human evolution.
- Humans and Neanderthals not only lived at the same time, but interacted and even mated. Learn more about it in a our post on Dr. Briana Pobiner’s work.