Dorsa Amir Profile picture
11 Jan, 10 tweets, 3 min read
I’ve recently been reading through “The Butchering Art”, a terrific account of 19th century surgery & the introduction of germ theory & anesthesia to Victorian medicine. I highly recommend reading it yourself, but here are some interesting tidbits that caught my attention (1/10)
(2) First, as you can imagine, early surgery was absolutely awful & almost always a last resort. One thing I didn’t realize was that back then, the best surgeons were the *fastest* surgeons — for instance, Robert Liston could remove a leg in less than thirty seconds (!).
(3) Early surgery was limited to “peripheral” conditions, like lacerations & fractures. This is because entering the body in surgery was almost always fatal due to infection. This led to the distinction of physicians practicing “internal medicine”, a term that still persists.
(4) More dangerous than the surgeries were post-operative infections & diseases. Four were particularly common — gangrene, septicemia, pyemia, and erysipelas — & were known as “hospitalism”. With the rise of early anesthesia came a rise in attempted surgeries & hospitalism.
(5) What’s wild about this era, looking back, is that no one really knew what was going on... but their theories made some sense. “Contagionists” thought disease was communicable, being transferred from person to person by “invisible bullets” or chemicals. Not the craziest idea.
(6) “Anti-contagionists” thought the opposite: they thought disease arose spontaneously from filth & was transmitted through poison air (“miasma”). Indeed, many terms like “malaria” come from this perspective = “mala” = bad, “aria” = air. This theory also seems plausible, no?
(7) Of course, the real answer, that disease can spread through tiny, invisible organisms sounds like borderline science fiction. Though some did think disease could be spread through “animalcules” — small organisms — germ theory didn’t receive widespread attention until Pasteur.
(8) In a cool experiment, Pasteur boiled liquid to kill off microbes, then used 2 flasks: an open-top flask & an S-shaped one that prevented dust from entering. He then showed that the S-shaped flask liquid remained uncontaminated. Microbes came from the air, not from the liquid.
(9) Inspired by Pasteur, Joseph Lister adopted the idea that it wasn’t *air* that caused infections, but rather microbial life *in* the air. He was among the first to suggest pre-treating wounds with antiseptics to prevent infection, as opposed to trying to control it afterward.
(10) I won’t give the entire book away, but suffice it to say it’s a fascinating read. I’m genuinely impressed at the advances science & medicine have been able to make into discoveries that are often stranger than fiction. Shoutout to @psmaldino for the book recommendation!

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More from @DorsaAmir

9 Oct 20
Culture can evolve rapidly, much faster than genes. Due to this, cultural changes can create new environments that in turn shape our genes. This is called “culture-gene coevolution” & there are some really cool examples of it in humans, especially when it comes to our diets. 1/
The classic example is “lactase persistence”. Most mammals can break down the sugar in milk — lactose — using an enzyme called lactase. But, in most species, this enzyme goes away around the time they stop nursing. Why is it that a third of adult humans can still digest milk? 2/
The answer is culture. In some "hot spots", people started herding animals. This opened up a new resource: animal milk. In at least 2 events, mutations that let people keep producing lactase were selected for. The variant in the Middle East is likely due to camel milk 🐫 3/
Read 6 tweets
15 May 20
In the ongoing battle against herbivores, some plants have evolved unusually clever defenses 🌿 Here are a few I find particularly interesting. (1/6)
Some plants pretend to be infested by aphids to keep actual aphids away. On the left is a branch of Paspalum paspaloides, with a number of dark anthers on it that look like aphids. Compare that to an actual aphid infestation on the right. A pretty compelling copy, no? (2/6)
In addition to growing spines and thorns to keep predators away, some plants enhance the effect with “automimicry” — copying the patterns of their spines on their leaves to look more ferocious. Below are a couple Agave plants showing off this trait. (3/6)
Read 7 tweets
27 Nov 19
Chess is one of the oldest games in the world — stretching back more than a millennia — and a fascinating example of cultural evolution ♟️ Here are a few snippets from its rich history. (1/7)
(2) Chess likely comes to us from India. The original name — chaturaṅga (चतुरङ्ग) — meant “four (military) divisions”: infantry, cavalry, chariotry, & elephantry 🐘 Indeed, the bishop was originally a war elephant & is still called so in many places. In Mongolia, it is a camel.
(3) From India, chess moved into Iran. Ancient Persians (c. 700-800 AD) introduced the idea of warning the other player when their King was under threat. The term “checkmate” comes from the Farsi term “Shāh Māt” (شاه مات) meaning “The King is helpless”.
Read 7 tweets
17 Oct 19
Ever wonder why humans are the only animals that need braces? 🦷 Turns out this is a relatively recent problem for us. (1/5)
If you look at the fossil record, you’ll find that our ancestors’ teeth look surprisingly good. While there’s some evidence for ancient dentistry using tiny flint tools (ouch), there was very little need for ancient orthodontists. (2/5)…
So what happened?

Well, to put it simply: industrialization. As our diets changed, so did our eating habits. We started to cook softer foods & eat with utensils.

This led to a big change: we stopped chewing as much. (3/5)
Read 9 tweets
26 Mar 19
There's a good chance that a bunch of the scientific ideas you’ve learned are now outdated and debunked. Here are some of the ones I feel most strongly about 👇 (1/7)
Are you an ENTP or an ISTJ? Turns out it doesn’t matter ¯\_(ツ)_/¯ The Myers-Briggs personality questionnaire has pretty poor validity & reliability. It's basically astrology. FYI, the "Big Five" is a way better personality framework. (2/7)… A listing of the different Myers-Briggs personality types.
You may have heard that women who live together start having their periods at the same time. Nope. This phenomenon, known as “menstrual synchrony”, is likely not real. A good review can be found here:… (3/7) A picture of two women together with the caption
Read 7 tweets
15 Jan 19
Did you know the human body is full of evolutionary leftovers that no longer serve a purpose? These are called vestigial structures and they’re fascinating. (1/8)
Put your hand flat on a surface and touch your pinky to your thumb. Do you see a raised band in your wrist? That there’s a vestigial muscle called the palmaris longus. It used to help you move around the trees. About 14% of us don't even have this muscle anymore. (2/8)
Check out your ear. Do you see this little bump? That’s called Darwin’s tubercle. It used to help you move your ears around. Now that we have super-flexible necks, we don’t need these anymore. (3/8)
Read 10 tweets

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