The meats available to our paleo ancestors came from paleo
animals who were eating properly for their own ecological
niche.  In a sense, it WAS leaner than the prime grain fed
beef in today's supermarket.  Those animals actually used
their muscles rather than standing around eating all the
time like the cattle in a feed lot.  There was less
marbling.  They had fat reserves, of course, and these were
utilized by our ancestors - pemmican is half fat.  But the
muscle and the fat was more separated then so the meat by
itself was leaner.  Perhaps this is what he means when he
speaks of lean meat.

--
   Elisi Tsayonah, AniWodi, ghigau,
   St Francis River Band of Cherokee