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Cake day: March 28th, 2024

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  • Just to preface, I’m a scientist: micro- and molecular biology. I’m not saying to take what I say as gospel, just giving context that I might know things. Sometimes.

    Outbreeding depression has more possible implications than fertility decrease and infant mortality increase, entirely dependent on the heritable traits responsible for the depression effects. While the probability of persistent outbreeding depression seen in subsequent generationa would be lower due to traits subject to higher selective pressure, like increases in early infant mortality, the overall probability of outbreeding depression itself isn’t influenced post facto by its results, just its persistence.

    Given we don’t know the original extent of neanderthal/human interbreeding, what we’re seeing now COULD be the “much lower percentage” you mention and still could come from multiple events. In fact, if these crosses resulted in stronger depression effects, I’d argue a greater number of crossings would be one factor behind the persistence of some genes today.



  • Two ways.

    First, sex chromosomes. In mammals, sex is determined by the sex chromosomes - males have XY, females XX. If interbreeding was equal between the sexes of both species, this would be reflected in the frequency of neanderthal genes on each chromosome in the current human population, but it’s more heavily skewed toward the Y chromosome than we’d expect if equal pairing was true. This suggests a higher proportion of successful male neanderthal/female human offspring.

    Second, mitochondrial DNA. While genomic DNA in a sexually-reproducing species is a mix between the parents, in most mammals the inherited mitochondrial DNA (mtDNA) is purely maternal. This is because only the egg’s mitochondria typically survive, though on rare occasion paternal mitochondria are also passed on. There is no known existent neanderthal mtDNA in the human population. This suggests either female neanderthal/male human crosses didn’t happen much and/or didn’t often produce offspring capable of further reproduction.

    Of course, there are many other explanations for all of these. These are just amongst the simplest possible options, and in population genetics, it’s not uncommon that the simplest answers are frequently correct.


  • Keep in mind heterosis isn’t always the result of hybridization and even then the magnitude of isolation doesn’t always positively correlate. Outbreeding depression can also be the result, increasingly so when two groups are more genetically distant or when one group is already subject to heavy inbreeding depression, as the neanderthals were thought to be.







  • Totally agree, it’s a harder to debunk way of protecting your time. Grandpa story time!

    I follow something I call the rule of thirds. Of any three unverifiable improvements in workflow, two remain secret and they and their saved effort are solely mine while the smallest goes to the company. If I bust out 12 in a row, the company gets the smallest four. Maybe three if I’m feeling catty. I occasionally dole out one of the retained 2/3 when I need to look good for a review or something.

    I learned this from an employer a few years back. I maxed out the first year and made a ton of improvements, so my first review was stellar. My second year’s review, though, noted that I hadn’t kept up with the previous year, so it was just a “meets expectations”. I was outperforming most of my peers, but not previous year me, so they thought I was starting to slack off. That’s when I realized many managers are idiots so you have to game the system if you want to succeed.