都市部としぶアライグマに家畜化かちくか初期しょき段階だんかいの兆候ちょうこう――鼻先はなさき短縮たんしゅくに見みる進化しんかの可能性かのうせい

According to research published by American biologists, physical changes suggesting the early stages of domestication have been observed in raccoons living in urban areas.

In particular, the characteristic of a short snout, which is often seen in pets and livestock, is becoming increasingly prominent in urban raccoons.

Associate Professor Ress at the University of Arkansas at Little Rock began to focus on the morphological differences between urban and rural raccoons after a chance encounter with a raccoon on the university campus.

According to Mr. Les, a hypothesis has emerged that urban raccoons are beginning to undergo domestication.

This idea is also based on past cases where garbage served as a driving force for domestication.

For example, wolves began searching for food around humans about 30,000 years ago, picking up garbage and leftovers, and over thousands of years, they were gradually domesticated.

Mr. Lesh states, Human existence has always been linked to garbage, and animals have adapted to coexist with humans by making use of it.

To investigate whether urban raccoons are gradually exhibiting signs of domestication, such as shorter snouts, Leshs research team analyzed approximately 19,000 raccoon photos submitted by citizen scientists.

The results indicate that the snouts of raccoons in urban areas are 3.6% shorter than those of raccoons in rural areas.

This difference is not very significant, but it is considered a clear sign in the early stages of domestication.

The series of traits known as “domestication syndrome,” which the father of Darwinian evolution observed since the 19th century—including short snouts, small teeth, floppy ears, curled tails, and patches of white fur—do exist.

According to an article from 2014, the process of selecting docile individuals affected embryonic development, resulting in a decrease in neural crest cells and pigment cells.

Mr. Les analyzes, Selective breeding for gentle temperament may cause changes in these cells, which could lead to the appearance of characteristics of the domestication syndrome.

However, Associate Professor Grossman of North Carolina State University points out that a shorter snout does not necessarily indicate domestication, and that it may be due to other factors.

Also, unlike other domesticated animals, raccoons do not have a unique social structure.

For example, wolves, sheep, and cattle have clear social hierarchies, but raccoons do not necessarily live in groups.

Nevertheless, Mr. Lesh believes that the process of domestication is highly flexible, and that even species with different social structures, such as stray cats and wolves, could potentially evolve in the direction of domestication.

In the future, the research team plans to continue analyzing the raccoon skull collection stored at the university and further verify their findings by comparing the behavior of raccoons in urban and rural areas.

However, at present, it is still difficult to confidently assert that the process of domestication is actually underway, and even if traits such as floppy ears, white spots, or curled tails were to appear over the next several thousand years, modern scientists would likely never witness the entire process firsthand.

Les said, It was highly meaningful to witness the beginning of this story of evolution and to be able to document it.