How Humans Shaped Chickens and Shrunk Foxes

Uncovering the Evolution of Animal Sizes Over 8,000 Years

A groundbreaking study conducted by archaeologists in southern France has provided new insights into how human activity has influenced the size of both domestic and wild animals over thousands of years. By examining bones that span an 8,000-year timeline, researchers have uncovered a fascinating shift in the evolutionary patterns of these species.

The Natural Cycle of Animal Size

Throughout history, the size of animal species has naturally fluctuated due to various factors such as environmental changes, resource availability, and evolutionary pressures. These fluctuations often occur in cycles, with some species growing larger and others shrinking depending on the conditions they face. However, this balance was disrupted when humans began to play a more active role in shaping the environments of both wild and domesticated animals.

A Shift in the Middle Ages

The research, led by scientists from the University of Montpellier in France, revealed that during the Middle Ages and the Modern Era (approximately 1000 to 2000 AD), the evolutionary trajectories of domestic and wild animals diverged significantly. According to Allowen Evin, one of the study’s authors, "wild species decreased in body size, while domestic species increased."

This change was particularly noticeable in several species. For example, foxes and rabbits became smaller, likely due to the loss of their forest habitats as human settlements expanded. Intensive hunting practices, which gained momentum during the late Middle Ages, also contributed to the decline in the size of these animals. Meanwhile, domesticated species such as sheep, goats, cattle, pigs, and chickens grew larger, reflecting the increasing control humans exerted over them through selective breeding and managed environments.

Environmental Pressures on Wild Species

The shrinking sizes of wild animals were not solely due to habitat loss. Other factors, including climate shifts and competition for resources, also played a role. As forests were cleared for agriculture and urban development, many wild species found themselves in increasingly fragmented and less hospitable environments. This, combined with the pressure of hunting, led to a general reduction in their body sizes.

Human Influence on Domestic Animals

In contrast, domestic animals benefited from human intervention. As societies developed more systematic approaches to farming and animal husbandry, selective breeding became a key factor in shaping the traits of these species. Farmers began to favor larger, more productive animals, leading to a steady increase in the average size of domesticated species over time.

A Comprehensive Study of Bone Remains

To gather their findings, the research team analyzed 225,780 bones from 311 archaeological sites across southern France, covering a period of 8,000 years. Initially, the project focused on domestic animals as part of a broader European Research Council initiative exploring changes in plants and animals over eight millennia. However, the discovery of a wealth of data on wild species prompted the researchers to expand their study, resulting in a large-scale comparison between the two groups.

Understanding Human Impact on Nature

Evin and her colleagues believe that studying the evolution of animals in relation to human development offers valuable insights into our own history. They argue that the influence of humans on the natural world has steadily increased over the past few millennia, with profound effects on ecosystems and biodiversity.

"Understanding our past — and how humans evolved and co-evolved with other species and their environments — is essential for understanding the origin and development of our modern societies," Evin emphasized.

This study highlights the deep and lasting impact of human activities on the natural world, underscoring the need for continued research into the complex relationships between humans, animals, and the environment.