It's an interesting concept that generalizations can be true without applying to every case. For example, the statement "humans have one heart" is generally tru

It's an interesting concept that generalizations can be true without applying to every case. For example, the statement "humans have one heart" is generally true, but there are exceptions where people have had an additional heart surgically added to assist a failing heart. Similarly, while it's common to say that humans have ten fingers, there are variations where some people are born with more or less, or have lost fingers due to accidents. Eye color is another example where we can't make a universal claim about humans. Although brown eyes are common, the number of people with blue or green eyes is significant enough that we can't say all humans have brown eyes. So, when we say "humans have X," it doesn't mean every single human has X. Rather, it means that a significant enough number of humans have X for us to consider it a characteristic of our species.