"הם בני אדם."
Translation:They are humans.
^this here. Duo (wisely) avoids religious topics outside of specific lessons, but it's hard to understand the linguistic concept of בני without at least a minimal understanding of the theological underpinnings of Hebrew, which include the notion of being born sons/daughters of patriarchs/matriarchs.
If I understand correctly, adam (lower case) means a human. People can be given the name Adam, but it’s not necessarily a proper noun. In this idiom, it is referring to the mythological first human with the name Adam, and then of course all humans are his children. Maybe it’s due to reading too much Narnia as a child, but “sons of Adam” to refer to humans seems like a perfectly normal thing to say, to me.