Have you ever seen bison up close? They’re big. Some stand six-and-a-half feet tall at the shoulder. They can weigh up to a ton and run 40 miles per hour. You don’t want a sharp-horned creature like that barreling across the plain at you! But no worries—these big fuzzy animals just want some grass to munch.

God’s creatures—both people and animals—are made to live in community. Often, the more variety in a community, the healthier its individual members are. Bison are supposed to live in small groups. But in summer, these groups should come together in huge herds to mate. Bulls (males) lock horns in fights for cows (females). Nine months after mating time, baby bison are born. Will the calves have good enough genetics to survive disease and bad weather? It probably depends on the size of the summer herd.

Genes determine an animal’s size and color. They might decide whether a cow will be better for dairy or beef, or whether a dog will be better for guarding sheep or hunting ducks. That variety is good. Sometimes scientists breed all the members of a population to be genetically identical. They do that so they can see clearly how substances (like new medicines) affect an animal. But in real life, the more variety the better.

Over time, a species’ genetics change. Animals adapt to their conditions. That’s one reason people have to be very careful while they’re doing “genetic rescues”—trying to improve the genepool of a group of animals in trouble. It’s important that animals with strong genes survive and animals with weaker genes die off. Humans need to make sure they help without interfering with God’s design for strong animals.

People watch the bison herds change. What new genes will help the animals thrive? One thing is sure: They’ll always be bison. God made animals “according to their kinds.” (Genesis 6:20) Genes never change so much that an animal becomes a new species.