[guard-of-terra]

They absolutely aren't! Mammals are Synapsids, reptiles and birds are Sauropsida. They branched before most of brain development in both groups took place and since then we don't share ancestors.

[biggfoot]

Hmm. Interesting. So there is absolutely no basis to a reptilian brain component thingie?

[guard-of-terra]

There might or might not be - we still have some our distant evolutionary ancestors; but the nice name for it ("lizard brain") is false.