 Selective breeding is also known as artificial selection. It is a process by which humans breed plants and animals for particular genetic characteristics. We have been doing this for thousands of years. Ever since we first bred food crops from wild plants and started domesticating animals about 10,000 years ago. This is when we made the transition from hunter-gatherers to farmers. We no longer needed to wander around to gather food supplies. Wheat, barley, lentils, peas, rice and potatoes were all cultivated by early citizens. We also began to tame animals for milk, meat and hides. Goats, sheep and chickens are thought to have been the first animals to be domesticated, followed later by bigger animals like horses and oxen for plowing and transportation. Agriculture allowed fewer people to provide more food. Regular, predictable food production led to increased populations and density of people. People now had the time to travel, trade and communicate. Settlements began growing. The first villages and then cities were both near fields of domesticated plants. Civilization was founded upon selective breeding. How does selective breeding work? Parents with the desired characteristics are selected from a mixed population and are bred together. From the offspring, those with the desired characteristics are then also bred together. This continues over many generations until all the offspring show the desired characteristic. Just think of all the breeds of dog that are around today. These were all selectively bred from a common wolf ancestor. The desired characteristics that we select for can be chosen for usefulness or appearance, such as insect and disease resistance in food crops by breeding from the naturally resistant individuals to increase yields, animals which produce more meat or milk to increase yields, domestic dogs with a gentle nature, large or unusual flowers. We just keep breeding and selecting and breeding once more. Until we hit the desired jackpot. Look at what we've done to modern chickens in 50 years. It's over four times bigger due to selective breeding. By inbreeding parents that are genetically closely related, negative outcomes can arise. The offspring will all share very similar genes, which could make some diseases more dangerous as all individuals would have the same weaknesses. The reduced gene pool also means that they are more vulnerable, as they have less chance of being able to adapt to changes in the environment such as climate change. There's also an increased risk of genetic disease caused by recessive genes. Being genetically very similar, if both parents carry the recessive gene for a genetic disease like cystic fibrosis, then the offspring will all inherit this disease. The white tiger is a good example of severe mutations boarding up due to the inbreeding of individuals that are too closely related. We have been selectively breeding for thousands of years, giving closer to our desired goal with each generation of offspring. Nowadays, we have come up with a faster way to do it, genetic engineering. We can transplant the gene for a desired characteristic straight into an organism. We will look at genetic engineering in more detail in another video. So there you have selective breeding. We have been doing it since the origins of agriculture, and aren't looking to stop anytime soon. We do, however, need to bear in mind the potentially negative outcomes, such as the loss of genetic variety, potentially making the species vulnerable to other diseases.