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posted by chromas on Monday August 10 2020, @11:14AM   Printer-friendly

Humans Might Be So Sickly Because We Evolved to Avoid a Single Devastating Disease:

Sialic acids are a diverse group of carbohydrates that blossom like leaves from the tips of proteins covering the surfaces of human cells.

[...] Changes in sialic acid markers can give rise to a number of diseases. But it was one specific change particular to all humans that the researchers here were most keen to gain an understanding of.

Most mammals – including closely related apes – have a compound called N-glycolylneuraminic acid, or Neu5Gc. We've known for some time that the gene for this version of sialic acid is broken in us, leaving its precursor form, N-acetylneuraminic acid (Neu5Ac), to do its job.

Researchers previously speculated that this mutation was selected for in humans to make it harder for devastating malarial parasites such as Plasmodium knowlesi to latch onto red blood cells.

[...] Since chimpanzees retain the gene for Neu5Gc, the mutation must have occurred within the past 6 million years or so, sometime after we parted ways from one another.

[...] This most recent study shows Neanderthals and Denisovans share our variant of sialic acid, meaning the change happened before our branch of the family tree separated roughly 400,000 to 800,000 years ago.

[...] To differentiate between cells that belong to us from possible invaders, our immune cells are armed with a scanning chemical called sialic acid-binding immunoglobulin-type lectins. Or Siglecs for short.

When an inspection occurs, if a cell's sialic acid marker isn't up to scratch, it's curtains for that cell. Naturally, any changes to our sialic acid name-tag would imply our system of Siglecs would have needed adjusting as well.

Sure enough, on further investigation the researchers found significant mutations among a cluster of Siglec genes that are common to humans and their ilk, but not great apes.

[...] Siglec expression is linked with conditions such as asthma and Alzheimer's disease, raising the possibility that protection from a devastating disease put us at risk of other conditions.

Journal Reference:
Naazneen Khan, Marc de Manuel, Stephane Peyregne, et al. Multiple Genomic Events Altering Hominin SIGLEC Biology and Innate Immunity Predated the Common Ancestor of Humans and Archaic Hominins [open], Genome Biology and Evolution (DOI: 10.1093/gbe/evaa125)


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  • (Score: 2) by istartedi on Monday August 10 2020, @06:09PM (6 children)

    by istartedi (123) on Monday August 10 2020, @06:09PM (#1034430) Journal

    This was apparently true for polio. I read something about how while it had always been a thing, it wasn't that common because toddlers played in the dirt. If you're a toddler it's apparently less likely to kill you. Then people moved in to situations where they played outside less, or in streets that didn't have soil with polio virus in it. As a result, they were exposed to the virus later in childhood when it had a worse outcome. The whole thing got really bad shortly after WW2 when that "clean house" lifestyle was being promoted; but I'm not sure if they ever documented a connection. Crowding in to cities probably didn't help either. Fortunately we got the vaccine so there was no need to learn more.

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  • (Score: 2) by Reziac on Tuesday August 11 2020, @02:59AM (5 children)

    by Reziac (2489) on Tuesday August 11 2020, @02:59AM (#1034699) Homepage

    Doesn't explain why polio persists in some of the dirtier countries; still endemic in Pakistan, Afghanistan, and Nigeria. Scroll down to the map:

    https://ourworldindata.org/polio [ourworldindata.org]

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    • (Score: 2) by istartedi on Tuesday August 11 2020, @07:19AM (4 children)

      by istartedi (123) on Tuesday August 11 2020, @07:19AM (#1034793) Journal

      Most likely that has little to do with cleanliness, and more to do with getting vaccines distributed to remote war-torn areas where people distrust the health workers who are distributing the vaccines--sometimes for very good reasons due to past unethical testing.

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      • (Score: 2) by Reziac on Tuesday August 11 2020, @01:08PM (3 children)

        by Reziac (2489) on Tuesday August 11 2020, @01:08PM (#1034882) Homepage

        That might explain Afghanistan, but not Pakistan or Nigeria.

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        • (Score: 3, Informative) by istartedi on Tuesday August 11 2020, @08:02PM (1 child)

          by istartedi (123) on Tuesday August 11 2020, @08:02PM (#1035119) Journal

          Here's a good read on Nigeria. [plos.org]. If you skim the top it just looks like garden variety anti-vacc, but the historical context and documented abuses are down towards the bottom.

          Pakistan has the disputed territory of Kashmir. It can't be easy to distribute vaccines there.

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          • (Score: 2) by Reziac on Tuesday August 11 2020, @08:34PM

            by Reziac (2489) on Tuesday August 11 2020, @08:34PM (#1035143) Homepage

            Ah, the relevant portion:
            ===
            “Since September 11, the Muslim world is beginning to be suspicious of any move from the Western world…Our people have become really concerned about polio vaccine” [14]. In the same article, Datti Ahmed, a Kano-based physician who heads a prominent Muslim group, the Supreme Council for Sharia in Nigeria (SCSN), is quoted as saying that polio vaccines were “corrupted and tainted by evildoers from America and their Western allies.” Ahmed went on to say: “We believe that modern-day Hitlers have deliberately adulterated the oral polio vaccines with anti-fertility drugs and…viruses which are known to cause HIV and AIDS”
            ===

            I knew this was going on in Pakistan (not Kashmir, the whole country) but had not heard that it had taken hold in Nigeria.

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        • (Score: 0) by Anonymous Coward on Tuesday August 11 2020, @08:11PM

          by Anonymous Coward on Tuesday August 11 2020, @08:11PM (#1035120)

          Pakistan and Afghanistan share a border, and have similar problems.