Some of it goes back to bacteria, some of it goes back to worms, some of it originated in the first mammals, some of it in the first primates, some of it in the first human beings. Very little of it, however, changed in the last 50,000 years.
Algunas partes provienen de las bacterias, algunos de los gusanos algunos se derivan de primer mamífero, algunos de los primeros primates, y algunos de los primeros seres humanos.