al. (2011) also reported evidence for strong carbon production in the early universe, based on their analysis of the optical spectrum of the most distant known radio galaxy, with $z$ = 5.19.

The mechanisms that have been proposed to account for this large carbon production include: (1) mass transfer of carbon-enhanced material from the envelope of an asymptotic giant branch (AGB) star to its (presently observed) binary companion (e.g., Herwig 2005; Sneden et al. 2008; Masseron et al. 2010; Bisterzo et al. 2011, 2012); (2) massive, rapidly rotating, zero-metallicity stars, which produce large amounts of carbon, nitrogen, and oxygen due to distinctive internal burning and mixing episodes (Meynet et al. 2006, 2010); and (3) faint supernovae associated with the first generations of stars, which experience extensive mixing and fallback during their explosions and eject large amounts of C and O (Umeda & Nomoto 2003, 2005; Tominaga et al. 2007; Ito et al. 2009, 2013).

This early carbon production can have a profound influence on the chemical evolution of the Galaxy and the universe. As argued by Abia et al. (2001) and Lucatello et al. (2005), and most recently by Suda et al. (2013), the large fraction of CEMP stars at 