04 September 2018

Is overpopulation a self-correcting problem?


Excerpts from an article in GQ:
Last summer a group of researchers from Hebrew University and Mount Sinai medical school published a study showing that sperm counts in the U.S., Europe, Australia, and New Zealand have fallen by more than 50 percent over the past four decades. (They judged data from the rest of the world to be insufficient to draw conclusions from, but there are studies suggesting that the trend could be worldwide.)...

The Hebrew University/Mount Sinai paper was a meta-analysis by a team of epidemiologists, clinicians, and researchers that culled data from 185 studies, which examined semen from almost 43,000 men. It showed that the human race is apparently on a trend line toward becoming unable to reproduce itself. Sperm counts went from 99 million sperm per milliliter of semen in 1973 to 47 million per milliliter in 2011, and the decline has been accelerating. Would 40 more years—or fewer—bring us all the way to zero?..

The results, when they came in, were clear. Not only were sperm counts per milliliter of semen down by more than 50 percent since 1973, but total sperm counts were down by almost 60 percent: We are producing less semen, and that semen has fewer sperm cells in it. This time around, even scientists who had been skeptical of past analyses had to admit that the study was all but unassailable...

Testosterone levels have also dropped precipitously, with effects beginning in utero and extending into adulthood...
One possible explanation:
When a chemical affects your hormones, it's called an endocrine disruptor. And it turns out that many of the compounds used to make plastic soft and flexible (like phthalates) or to make them harder and stronger (like Bisphenol A, or BPA) are consummate endocrine disruptors. Phthalates and BPA, for example, mimic estrogen in the bloodstream. If you're a man with a lot of phthalates in his system, you'll produce less testosterone and fewer sperm.
More at the longread link.

6 comments:

  1. Classic scare article and likely unadulterated BS. Correlation is not causation. Sperm count isn't hard data. Yes, hormonal toxicity of trace chemicals is a thing, as well as a million other environmental factors, like nutrition, obesity, air quality, noise, EM/Microwave emissions.

    Even taken sperm at face value, I would instead suggest to correlate the article with the wide availability of prngraphic materials, which affect sperm count much more directly, lowering it... into a tissue.

    Ad hoc explanations aside, infertility will never become an issue for any species. Fecundity is the one thing that evolution excels at.

    I'm looking forward to more articles from GQ, like "aren't we becoming to smart and contemplative?" and "We should spend more time staring at our 1k$ phones, to make sure the purchase pays off." and "Are Electrolytes soluble healing crystals?"
    Disclaimer: I've never read GQ, nor did or would I read that article. It's just a wild guess.

    ReplyDelete
    Replies
    1. *sigh* I don't even know where to begin.

      Apparently you don't even have the basic understanding that the research wasn't conducted by the staff at GQ magazine or published by them. GQ cited the research because its readers are interested in male sexualilty.

      But of course "never... would you read that article." Why would you read it? You already have extensive knowledge on the subject. You base your absolute dismissal of the data based on your preconceived notions of what must or must not be true.

      If I give you the abstract from PubMed (NIH), would that help?

      https://www.ncbi.nlm.nih.gov/pubmed/28981654

      Probably not. You already have averred that masturbation is more likely as a cause of lower sperm counts [wrong] and that such a factor would not have been considered by academic reproductive endocrinologists.

      Do you even understand that the data referred to was not a study but a "meta-analysis" ? Do you know what a meta-analysis is? No. You prefer to offer proclamations based on "a wild guess."

      Apparently a "classic scare article" is one that has reviewed 7,000 abstracts and 2,500 articles reporting primary data. But it doesn't agree with your worldview, which makes it "unadulterated BS."

      I can even predict your political tendencies and your party affiliation. At least you didn't call this "fake news."

      You're on the wrong blog, dude.

      Delete
    2. @Minnesotastan: Look at it this way, you may rate high enough to warrant your own Russian trolls.

      Delete
    3. I've gotta say, that red line in the graph is suspiciously linear...

      Delete
    4. That reply was absolutely beautiful Minnesotastan. Thank you.

      Delete
    5. Thanks for replying and linking the abstract. To be fair, I was honest and actually argued the case, explaining why I feel secure dismissing something unread.

      A scare article is something that takes some fact, or trend and extrapolates it baselessly into a scare, "Sperm count is declining, surely it will reach "0" in 40 years!"

      1. Problem is it is still the same order of magnitude 338 M - 138 Million, it may not even be a significant change. Those are big numbers, that are extrapolated from small counts and changing testing methods, older methods presumably actually counting cells under the microscope. But I don't doubt the numbers, I called BS on the explanation and extrapolation, neither of which are part of the study.

      2. Second problem - Averages. Even a standard distribution takes 2 variables (mu, sigma) to describe. Which is why only taking an averages can be misleading. It's possible that an industrial softener for plastics causes cancer in distant offspring and lowers their sperm production even in early stages. This will lower the average, but will not affect survival of the species if it only affects a fraction of men. However writing about how some guys might get cancer, people naturally assume themselves the exception...
      Anyway averages simply don't say much. The study uses this to ask for more research, which isn't unusual.

      3. The explanation is unknown (and thus stated in the article), virtually impossible to verify (because of the decades passing between cause and effect) and difficult to control for, especially in the meta-study. If you are doing a meta study how do you control for obesity, for instance? Do you throw out all the data that didn't take weight/BMI into account. That is the issue: A meta analysis cannot control for much of anything, meaning you can't really exclude any possible influences. It's a summarizing look at absolute numbers and trends, it can't isolate or hone in on any specific causes.

      Personally my biggest worry with plastics is their halogenated variety (vinyl) and the resulting virtually indestructible and yet toxic dioxins.

      Delete

Related Posts Plugin for WordPress, Blogger...