People make animals evolve faster

As a superior predator, humans force animals to change their body size and reproductive age at a rate three times faster than the natural effect.

Reindeer is one of the species that has the fastest rate of body size due to being hunted by humans.Photo: CBC.

Animal hunting on land and fishing has a great impact on the animal world. According to many experts, for animals, two human activities are even more frightening than natural disasters.

An expert group from the University of California (USA) analyzed 34 animal studies to understand the impact of hunting and fishing on animals. The object of these studies is 29 species in 40 geographic regions of the world. They found that the most hunted species of humans have a very small body size. On average, after each generation their body size is reduced by 20% and the age of first childbearing is also shortened to 25%.

'The hunted animals are much faster to shrink their body size. That may be because during the hunt, humans like the biggest ones to destroy. So animals have to shrink in size to not get into our sights , 'said Chris Darimont, lead researcher.

Some biologists believe that shrinking body size and accelerating reproductive age is not an evolutionary change because they do not detect changes in animal genes. The tendency to reduce body size not only occurs in large animals like deer or elephants, but also in small species such as fish and snails.

The findings of Chris Darimont and colleagues correspond to the results of many scientific works over the past two decades. In 1990, a study showed that 'selective hunting' behavior (selecting only the largest ones) caused a decrease in Kodiak body size (with brown hairs, living in the Alaska area of ​​the US). year by year.

The size of the brown bear in Alaska decreases year by year due to indiscriminate hunting.Photos: National Georgraphic.

The author of the study confirmed that the selective hunting behavior of humans caused the number of individuals of large size to decrease very fast, forcing smaller sized animals to reproduce sooner to compensate. amount. 'As a superhuman predator, humans play a big role in the evolution of the world' , Chris Darimont commented.

Chris affirmed that animal changes happen in a lifetime. 'Excessive hunting by humans has awakened the ability of animals to change , ' he added.

According to Chris, the changes take place in two ways. First, small animals have a better chance of survival when faced with humans (the smaller the fish, the easier it is to escape the net). When reproducing, they will pass the gene to the next generation. According to the law of creation, genes that are beneficial for survival will be retained. Thus, genes that regulate small body size and early reproductive time will be transmitted over generations.

The second change process is called flexibility. For example, species that breed in the fall try to give birth in the spring because it is a time when food is abundant. Due to eating more, the animals of the animals will get up early and reproduce in the spring.

'Accelerating the reproductive age creates many problems for the number of each species. Early reproductive individuals often produce fewer children. If we destroy too many individuals in a species, their fertility will decrease, from which the rate of recovery of their numbers will decrease , 'Chris explained.

Cod on the east coast of Canada is the best example of the trend of accelerating reproductive age. Nearly two decades ago, they started breeding in their sixth year, but now they give birth to their fifth year of investment to cope with overfishing.