Evidence for the Existence and Early Origin of Genes Making Possible the Darwinian Evolution of Biogeochemical Homeostasis at a Planetary Scale

Abstract

This paper uses empirical evidence to address the subject of when and how the processes for the homeostatic influence of the biota on planetary-scale biogeochemical processes first arose. From Lovelock (1972) this planetary-scale homeostatic influence has been referred to as Gaia and we also do so in this paper. To set the scene for the study, the paper first proposes three core necessary attributes for Gaia: (1) individual organisms possessing control systems using feedback loops to regulate their external environment (the _environmental regulation_ core attribute); (2) joint action of groups of such organisms leading to the achievement of larger scale environmental regulation (the_ joint action_ core attribute); and (3) such action occurring at a planetary scale. The paper next identifies representative examples in contemporary organisms of each of the two non-planetary core attributes of Gaia in operation. For each of these examples, genes making up part of the genetic specification of the example were identified. We then sought these same genes in the earliest examples of life that have been genetically characterised in empirical terms - the Last Universal Common Ancestor (LUCA) and the Last Bacterial Common Ancestor (LBCA). These arose respectively between 4 and 3.5 billion years ago. Examining both the pools of known modern genes and demonstrated LUCA and/or LBCA genes, a number of modern genes related to functionality analogous to that of Gaia core attributes were also found likely to be in LBCA and/or LUCA. In other words, the potentiality for the eventual evolution of Gaia arose between 3.5 to 4 billion years ago. The paper also provides case studies showing similar results at increasing scales of organismal aggregation over the intervening period to the present. Doolittle (1981) and Dawkins (1982) stated, in essence, that it was impossible for them to imagine any evolutionary way by which Gaia could have arisen. Dawkins (1982) defined Gaia as was at the time predominantly done in terms of its planetary attribute. This posits that there is _one _Gaia on Earth. Dawkins pointed out that neo-Darwinian natural selection requires competition between _multiple _units of selection. Given the absence of such multiple units of selection, Dawkins proposed that Gaia could not come into being by neo-Darwinian natural selection. The Doolittle and Dawkins positions were influential and interpreted by some as evidence that Gaia could not exist at all. The evidence of the present study is that genes for processes analogous to the non-planetary core attributes of Gaia have been available from near the start of life. With such genes being units of selection, planetary Gaia could come about by a series of developments commencing near the start of life, each involving standard gene-based Darwinian natural selection. We consider these results to resolve the issue raised by Doolittle (1981) and Dawkins (1982).