Posted by:
[|]
(
)
Date: November 01, 2023 07:13PM
The prediction that the Y chromosome will disappear seems to be based on the assumption that loss of genetic material will continue at the same rate in the future as it has in the past.
Here are studies suggesting otherwise (they are technical)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4120474/"The process of Y chromosome degeneration has prompted the suggestion that continuing gene loss will lead to the eventual disappearance of the human Y80-83. These predictions are based on a naive model of a constant rate of gene loss from the Y chromosome. However, recent theoretical and experimental studies have clearly demonstrated that Y degeneration does not proceed in this simple linear fashion21,84, and refute these sensational claims of human Y extinction (Figure 3)."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3292678/"We discovered that, during the last 25 million years, MSY gene loss in the human lineage was limited to the youngest stratum (stratum 5), which comprises three percent of the human MSY. Within the older strata, which collectively comprise the bulk of the human MSY, gene loss evidently ceased more than 25 mya."
"In our reconstruction, strata 1–4 had already reached a stable level before the human lineage diverged from rhesus; after divergence from rhesus, gene loss in the human lineage was limited to stratum 5, the youngest stratum, which stabilized before the human lineage diverged from chimpanzee."
"Our empirical reconstruction of MSY evolution is at odds with a linear model7,9,10 and with a simple random decay (exponential) model25, both of which project a continual decline of MSY gene content and cannot account for the stability of gene content that we observe over the past 25 million years (Fig. 3). Our data are better explained by more complex models for MSY gene loss that incorporate a combination of evolutionary forces."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2475751/"Further, while degeneration can proceed very rapidly on newly formed Y chromosomes (or whenever new strata are added to the Y), the rate of degeneration by both positive and negative selection models eventually diminishes and becomes exceedingly slow on ancient gene-poor Y chromosomes. For example, at the rate of degeneration inferred for the mammalian Y, the human Y would still have ∼20 genes left in another 300 MY (Figure 9). Of course, the continued accumulation of new genes via additional autosomal fusions or transposition (Graves 2006) will also contribute to maintaining active genes on the Y chromosome. Moreover, if some of these genes are essential for males (i.e., sd = 1), the probability of losing such a gene would be extremely small (Crow and Kimura 1970). These considerations imply that predictions of the future loss of all functional genes on the human Y chromosome within 10 MY (Aitken and Marshall Graves 2002; Graves 2004, 2006) are not supported by theoretical models of Y chromosome degeneration. Instead, evolutionary theory suggests that the Y chromosome of humans is likely to survive for the foreseeable future."