DS6 asked yesterday why we have toenails. I explained it's likely a remnant of evolution and eventually people might be born without toenails, since they really have no use.
I asked DS5 who is sitting at the table coloring a string of paper dolls. He says that if we didn't have thumbs we wouldn't be able to pick up very many things. Then he experimented and found he could pick up his marker with just his fingers but it was difficult to color carefully.
DS7: "We'd have to go like this" [lifting yogurt cup with both hands and no thumbs] "instead of like this." [lifting yogurt with one hand] "And brushing teeth would be hard."
DS4: "We'd have to do this" [pushing with fists together] "to squeeze stuff out."
ds5. "I will answer that in a minute... What happens if our thumbs are like our big toes and not opposite(sic).. We couldn't count to more than eigteen, do this(picks up various books with two finger, we are in a public library). Mummy I am going to write a list of things like that.."