If Sleep Evolved Before Brains as the Hydra seems to show, What then is the Function of Sleep? 2021-05-20 Jorma Jyrkkanen jormabio@hotmail.com

If sleep evolved before Brains as the Hydra seems to show, What then is the Function of Sleep? 2021-05-20 Jorma Jyrkkanen jormabio@hotmail.com I have a hypothesis. Sleep evolved to reduce cortisol so that anti inflammatory cytokines would reduce inflammation and foster tissue healing from the ravages of a day of struggle for existence. The trail of evidence. How ancient is cortisol? Well it is present in bony fish, the teleosts, so is as ancient as they are. This means cortisol was present at least 160 Mya. But Hydra have even greater antiquity. Hydra (/ˈhaɪdrə/ HY-drə) is a genus of small, fresh-water organisms of the phylum Cnidaria and class Hydrozoa. They are native to the temperate and tropical regions. Biologists are especially interested in Hydra because of their regenerative ability – they do not appear to die of old age.They may have a cortisolo analogue but not the hormone itself. Cortisol has been reported in tissues of mollusks and crustaceans (Summavielleet al., 1995; Boseet al., 1997) suggesting a common ancestor to mollusks and crustaceans and teleosts had cortisol. Suffice it to say this hormnone has great antiquity. What then is its function in humans? High cortisol prevents anti inflammatory cytokine production leading to slower healing. Do we need a brain for this effect? Probably not. But if we can have a good sleep without stress cortisol might drop and real healing can take place for damage accrued through a hard day. Cortisol apparently evolved from steroid hormone receptors that only recognized estrogen when two mutations which enabled receptors to recognize hormones like estrogen, testosterone and cortisol (Joe Thronton, U of C, Junre 24, 2013). The p53 TSG gene spends a goodly amount of time sending defective cells to the dustbin and so does the immune system in wrapping up and digeting germs and worms and the ubiquitin proteasome system is busy as well in maintenance of a healthy cellular and tissue environment. All of this activity produces a fair amount of trash that has to be taken out. Sleep enables energy to channel to this task and heal the damage of a day of struggle. I am left with the hypothesis that when we sleep, cortisol levels drop enabling anti-inflammatory cytokines to help with healing and all these other repair mechanisms. Elevated cortisol levels are negatively associated with wound healing and probably cell repair and p53 gene and ubiquitin proteasome garbage removal. We owe this ability to two mutations 500 mya and sophisticated TSG genes, immune system evolution and the UPS. When proteins are made there are a lot of mistakes that have to be shredded. Molecular evolution is essential for higher life evolution.