First Human Giatrus was an anime series about a prehistoric family set in the stone age, based off a manga by Shunji Sonoyama, the anime lasted from October 5, 1974 to March 27, 1976 produced by TMS Entertainment and aired on TBS (Tokyo Brodcasting Service) in Japan.
Ocean Studios (a.k.a. Ocean Productions Inc.) produced a pilot for the show under the name "The First Family" featuring voices of Matt Hill, Richard Newman, Teryl Rathery, and Terry Klassen. It's unknown if this was aired.
The TMS Entertainment English website has a listing of works, with English titles and logos (i.e., Ganso Tensai Bakabon is called Meet the Boneheads, although besides TMS's Malaysian dub edits (https://www.youtube.com/watch?v=8aI6PLCbqVY) there's no evidence for an actual English dub.
However, the TMS website has Giatrus, the First Man listed, and has a sample video embedded, which may not work on most browsers, being a .wmv file, however, streaming it to VLC or other media players with streaming capabilities, can allow you to watch it:
Here it's named The First Family, and was produced by Ocean Studios. Enjoy!
It shockingly has the right nipple of the mother character uncensored.