Did cavewomen, and ancient women in general, have larger or smaller boobs than we currently do?

Or has there been no change? I was remarking to my boyfriend yesterday how it’s interesting that humans are the only animal with BOOBS all the time. For example, when a dog has puppies and is lactating, the teats get full and sag a little bit but they don’t always have them….so why do we? Did we always have them? Are they getting larger or smaller? Why?