One of the first human foods was actually bone marrow which is basically pure fat. This happened about 2MYA by Homo habilis who figured out that you could use rocks to bust open bones. Lions and Hyenas would leave huge piles of bones in the middle of the dessert which had been picked clean by vultures. One of our ancestors had the brilliant idea to use a rock to bust open the bones. Well it's a massive source of free…
Most carnivores use their teeth to crush bones - lions and hyenas both do it. Heck, we buy doggie treats related to marrow and I have watched my own dogs crush bones to get to the marrow.
Marrow is quite accessible to all, including me - omnomnomnomnom.