A population or individual that is the result of an attempt to reproduce the morphotype or even the culture and behaviour of some past clade, race, or local population. This may be there result of fashion, ideology, or experimental curiosity. It may be the choice of an individual who wishes to attempt the conversion, or that individual's parents, or of an institution or government or a transapient. The term most often refers to individuals or groups that resemble past human baseline or nearbaseline groups.
There are many persons, tribes, or entire nations or planets scattered across the Terragen Sphere that to one degree or another resemble aboriginal Agricultural Age Scandinavians, Bantus, Mayans, Maoris, !Kung, Mongols, Mbuti pygmies, Andaman islanders, or Interplanetary Age gengineered Martians and Lunarians, or the unique human groups that developed in isolated habs during the Nanoswarm Age or in the early Interstellar Era colonies, or any of the myriad human baseline or nearbaseline groups that have arisen since. While replicas of baseline to nearbaselne human groups are the most common, "retro abo"; may also refer to similar movements regarding other clades, including certain "classic"; designs for human superiors or cyborgs, or even for vec, provolve, xeno, and ai clades. In particular, To'ul'h retro abo groups based on diverse populations of baseline To'ul'hs from To'ul'h Prime's long and varied history are perhaps the largest single rival to human retro-abos in diversity and number.
The degree of "authenticity" in retro-abo individuals and societies varies quite widely. It is usually rather low, particularly in attempts to reproduce the look of baseline human groups or early provolves, since if the re-creation were exact the resulting individuals are a good deal less capable than the typical modern sophont. Most often the underlying intelligence, strength, and health are greater than in the originals, and even the appearance is some idealized version, not the average for persons from that historical period. The relatively few highly authentic retro-abo groups are found in Baseline Reserves or in simulations of past historical periods, in which case the "abos" may not have consented to their condition in the first place and may be unaware of the larger galactic society.
Re creations of fossil and prehistoric groups are not usually considered retro abo; the various clades, of varying degrees of authenticity, resembling Homo sapiens neanderthalensis, or even archaic forms of Homo sapiens sapiens such as "Cro magnons"; or other groups are generally considered to be gengineered lazurogened persons instead.