from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The consumption of one embryo by another in utero; particularly as it relates to certain amphibians, sharks and fishes.
From Ancient Greek ἀδελφός (adelphos, "brother") and the suffix -φαγία (-phagia), combining form of φαγεῖν (phagein, "to eat") See also suffix -phagy. (Wiktionary)
He believes that mankind in its development went through a scary stage of adelphophagy, which literally means "eating one's brother."