Adam’s rib: Pheromones and the adaptive evolution of human sexuality

Adam’s rib, revisited: Evolutionary divergence of mammalian sex chromosomes

The article linked (above) may be of interest in the context of my comments and response to commentary linked below.

“Simpler life doesn’t have chromosomes. It has DNA rings and those rings can be captured from other organisms. Either by non-hostile exchange or eating each other.”

I don’t think ingestion of heterospecific DNA by microbes is widely known, and was reluctant to suggest it as a precursor to the self / non-self recognition that accompanies the adaptive evolution of sex differences in yeasts. But, I did in: Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors.

Here’s the section head and excerpted text from:

An epigenetic continuum from microbes to humans: from theory to facts

“Among different bacterial species existing in similar environments, DNA uptake (Palchevskiy & Finkel, 2009) appears to have epigenetically ‘fed’ interspecies methylation and speciation via conjugation (Fall et al., 2007; Finkel & Kolter, 2001; Friso & Choi, 2002). This indicates that reproduction began with an active nutrient uptake mechanism in heterospecifics and that the mechanism evolved to become symbiogenesis in the conspecifics of asexual organisms (Margulis, 1998). In yeasts, epigenetic changes driven by nutrition might then have led to the creation of novel cell types, which are required at evolutionary advent of sexual reproduction (Jin et al., 2011). These epigenetic changes probably occur across the evolutionary continuum that includes both nutrition-dependent reproduction in unicellular organisms and sexual reproduction in mammals. For example, ingested plant microRNAs influence gene expression across kingdoms (Zhang et al., 2012). In mammals, this epigenetically links what mammals eat to changes in gene expression (McNulty et al., 2011) and to new genes required for the evolutionary development of the mammalian placenta (Lynch, Leclerc, May, & Wagner, 2011) and the human brain (Zhang, Landback, Vibranovski, & Long, 2011).”

My academic and commercial interest in this complex ability in bacteria that suppress reproduction with pheromones when insufficient nutrients are available led me to sponsor the video game “Bacillus.” One entitlement is that I get to name an organism and attribute to it a characteristic. If a named organism eats the DNA of other bacteria, I named it!  If you want to encourage others to have some fun while learning about the  molecular biology of sex differences,  there is still time to contribute to the game’s development and get credit for doing so.



Author: James Kohl

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