Given that proteins are present in modern condensates, and chemically, peptides (simplistically, minimalized proteins) could have also led to primitive coacervate assembly. Peptides could have potentially been abundant on early Earth, as they could have polymerized (such as through volcanic gas, mineral surface catalysis, or dehydration synthesis ) from amino acid monomers that could have themselves arisen from hydrothermal synthesis, spark discharge, UV irradiation, or meteoritic delivery on(to) early Earth. The key feature of peptides used as building blocks for coacervates lies in the functional and chemical diversity of the amino acid residues available in the peptides (of course, constricted by availability on early Earth). For example, peptide formation in the cell generally results when the proteinogenic amino acids are biosynthetically incorporated into a growing chain through the translation system, but there non-proteinogenic amino acids (e.g., ornithine, citrulline, gamma-aminobutyric acid, etc) also exist; these are either not incorporated into proteins or not produced directly and in isolation by standard cellular machinery. However, while early peptides like contained some amount of proteinogenic amino acids, there's also the possibility (or, some would argue the likeliness, given the diversity of amino acids on early Earth ) of early peptide-based coacervates being composed of peptides with non-canonical amino acids formed by spontaneous abiotic synthesis. In particular, ornithine (a nonproteinogenic basic amino acid) is proposed to have been in early proteins, yet were "removed" over chemical evolution in modern proteins, possibly due to the selective incorporation of proteinaceous amino acids into growing primitive peptide chains. Poly-ornithine in particular has even shown the plausibility to phase separate upon binding with a synthetic anionic polymer, suggesting that although many studies on peptide-based coacervates focus on those with canonical residues, that peptides with noncanonical residues may also have significant phase separation propensity and novel functions yet to be discovered.