Why haven’t farm animals evolved against humans? A biologist explains why there won’t be a chicken uprising anytime soon

Alida de Flamingh, University of TennesseeCurious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com.Why haven’t farm animals evolved to protect themselves against humans? – Sarang, age 15, Latur, Maharashtra, IndiaHave you ever wondered why dogs get the zoomies or wag their tails? One answer comes from a rather unexpected source: foxes.A team of scientists bred captured silver foxes for tameness, choosing the least fearful and aggressive animals to become parents. They repeated this process with each litter of pups, avoiding any training and limiting their exposure to people.Lyudmila Trut was one of the scientists who developed the domesticated silver fox in an experiment that began in 1952 and continues today. Lee Alan Dugatkin/Evolution: Education and Outreach, CC BY-SAWithin six generations, the foxes began to show some familiar, doglike behaviors. Some wagged their tails as people approached, licked their hands and even liked to be petted.These silver foxes are a remarkable example of selective breeding, where people choose animals with particular traits to produce the next generation of animals.Selective breeding is the driving force behind domestication: the process through which animal populations adapted to life alongside people over many generations. Dogs are considered the first animals that humans domesticated, originally descending from wolves.Domestication and evolutionAnother team of scientists studied the genes of ancient animals to understand how domestication has shaped farm animals over time. They examined the genetics of a wide range of traits, from coat color in goats and horses to aggression and egg production in chickens.Farmers might selectively breed chickens for more eggs, or cows for more milk. They may also favor calmer animals because they are easier to handle. Because animals with these traits are chosen more frequently by farmers for breeding, their genes have a better chance of reaching the next generation.Dairy cows are bred for their ability to produce milk. Michael Fousert/Unsplash, CC BY-SAThis process is domestication in action: Inherited traits such as tameness, producing more food or having a coat color preferred by people become common over generations.Farm animals that are aggressive or don’t produce much food may be less useful to humans, thereby “protecting” themselves from being used by people. But with people in charge, these animals will also likely be excluded from breeding and have less of a chance of passing their genes on.On the farm, people hold all the power. Because of the process of domestication through selective breeding, farm animals cannot evolve to protect themselves from humans.Human influence in the wildPeople can influence evolution in the wild even without deciding which animals to breed.Animals with traits that help them evade humans who are trying to hunt or capture them will tend to pass on their genes to the next generation. This means that, in the wild, animal populations may evolve more protective characteristics, since people aren’t directly involved in selecting which animals will breed and pass on their genes.Consider the elephants of Gorongosa National Park in Mozambique, a species I study in my work as an evolutionary biologist. During the country’s civil war, poachers hunted large numbers of elephants for their ivory tusks.Female African bush elephants evolved tusklessness in response to human poaching. Gorgo/Wikimedia CommonsSome females were naturally tuskless, making them less likely to be targeted. As a result, these tuskless females had a better chance of surviving, reproducing and passing on the genes associated with tusklessness. Over generations, tusklessness became more common in the population.While these elephants did not deliberately evolve a defense against hunters, tusklessness provided a survival benefit. Therefore, evolution favored an existing trait that offered some protection.From friendly foxes to tuskless elephants, human choices can shape how animal populations evolve. Sometimes people do this deliberately, by breeding animals for desired traits. Other times, human impact on the environment alone can change which animals survive and reproduce, and therefore shape how species evolve.Next time your dog snuggles up, remember those foxes!Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.Alida de Flamingh, Assistant Professor of Evolutionary Genomics, University of TennesseeThis article is republished from The Conversation under a Creative Commons license. Read the original article.