![]() He grows up stronger and is able to gather more food and help raise more young. Long-bill allows this bird to eat fruit that was too hard to handle before, enabling it to access a nutritious and plentiful resource. Every once in a while, a new trait pops up that provides an advantage. This chick is totally safe from predators and it lives twice as long as everyone else.īut suppose the shield gets in the way and makes it physically impossible to breed.Įven though the individual survives to a ripe old age, the Armored Shield genes die off. So the genes that caused Awkward don’t make it into the next generation.Īrmored Shield seems at first to be beneficial. It’s hard to get around and forage.Ī baby born with the Awkward trait won’t grow up as strong as other chicks and might even die before it has a chance to breed. Like most new traits Awkward isn’t helpful. Here are three hypothetical new traits that might appear: Awkward, Armored Shield, and Long-bill. In every generation, due to recombination or mutation, some chicks are born with changes in their genes that cause them to grow up with traits that are a little different. Let’s start with a representative everyday bird from a small population living on an island. ![]() Then we’ll show how sexual selection can change the same population in unexpected ways. ![]() To understand how sexual selection can make an animal like this, we need to simplify things.įirst we’ll show how natural selection favors some traits over others and how that results in changes to a population. Sexual selection is about out-competing, often out-attracting competitors to get more and better mates, and that’s where the dancing and ornaments come in. The battle to breed generates a particular kind of selection called sexual selection. Well, natural selection isn’t actually the competition to survive: it’s the competition to pass on genes. Why do some have oversized ornaments making it harder to fly and forage? Why do some birds spend time and energy frantically dancing? ![]()
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