A few million years ago, our ancestors started walking upright. Big mistake! (Only slightly kidding). Bipedalism helped us a lot: it freed up our hands to use tools & engage in cool new behaviors. But it also came with a lot of costs, many of which we're still paying today (1/7) First up: pain! My god, the pain. Usually in the back, knees, & ankles. These are some of the most common health issues & bipedalism is largely to blame. Walking upright places extra stress on our poor bodies, which are constantly aching under the strain & weight. (2/7)

I'm a developmental scientist who studies how children grow & learn across cultures. I'm also an American mom who feels the extreme pressure put on parents in the West. I'm here to offer you some parenting ANTI-advice — here are a few things you can worry less about: 1/🧵 First: not everything has to be "educational". It's truly completely okay (& indeed, good) for kids to play for the sake of play. They don't have to be learning the alphabet or animal noises. They can just do whatever silly thing they want to do. They are ALWAYS learning! 2/

Protests continue in Iran today after #MahsaAmini's death in custody at the hands of the 'morality police' for violating the mandatory hijab laws.

How did we get here? The story is my family's story, and mine, too.

A personal history of women's oppression in Iran. 1/ Some background. It's 1952. Mosaddegh is the democratically-elected leader of Iran. Iran's oil is largely controlled by foreign interests. Mosaddegh fights back & dares to nationalize the Iranian oil industry. The West is angry; they organize a coup. 2/ npr.org/2019/01/31/690…

Slides are visual aids that assist your presentation. Anytime you put something on your slides, its primary purpose is to help the *audience*, not you.

Nothing should distract from your verbal presentation, it should only enhance it.

A mini-presentation on slide design. 1/ One common mistake is to clutter the slide with lots of text, which the speaker reads out to the audience, verbatim. This is a bit boring and inefficient. Condense down the text to the main question or point of the slide, and speak the rest. Scary, maybe, but you can do it! 2/

I didn't want to dignify this with a response but this thread is toxic — filled with inaccuracies, stereotypes, & the dumbest takes possible. I think almost every single point is wrong, actually, & extremely harmful.

Anthony, if you had any sense, you would delete this. 1/

https://twitter.com/dranthonygustin/status/1506996684756193280

First of all, the trope that hunter-gatherers are "wild humans" is flawed, harmful, & condescending, and the idea that they have "full genetic expression" is literally so stupid I don't even know where to start. They're.. expressing more genes than us? 2/

https://twitter.com/dranthonygustin/status/1506996687977398280?s=20&t=XimiWU3KjFZXwLTLnvDJ7w

When imagining the past, people tend to forget that a huge portion of the population was made up of children — playing, learning, getting into mischief, & sometimes even making art. Here are a few lovely & lively examples of children's art from the historical record 🧵 1/ First up are these (newly discovered!) tiny handprints, found in Tibet & dated to around 200,000 years ago. They seem to be intentionally made by at least two kids — probably between 7-12 years old — who found a layer of soft travertine & decided to leave their marks 🤚 2/

Ever wonder how monkeys ended up in the Americas? Did they cross over land bridges like we did?

The answer is no. They did something even wilder: they floated across the Atlantic (!) millions of years ago. Yes, really.

Let’s talk about oceanic dispersal! (1/5) So, how did the monkeys pull this off? Well, what happened is called a "rafting event": a piece of earth breaks off, with its flora & fauna intact, & essentially turns into a small floating island. In the Oligocene, the continents were closer, so the journey was shorter. (2/5)

We take for granted the fact that, whenever we want, we can see an unbelievably detailed image of ourselves in the mirror🪞 But consider that for the majority of human history, you were never able to actually, really see yourself. A thread on the humble, magical mirror. (1/9) The first mirrors were likely pools of still water or vessels that held reflective liquid, but in the Neolithic, we start seeing evidence for physical mirrors, like this incredible obsidian mirror from Çatalhöyük in Turkey, dated to approximately 7500-6400 BC. (2/9)

Humans have long needed a way to keep track of numbers as they count. In many cultures, finger counting is common. If you live in the United States or China, you probably count to five like this, but there are many different ways to achieve the same goal. (1/8) Variations of five-finger counting exist all around the globe, and between languages, as well. The Pekai-Alue in Papua New Guinea are notable in that the folded, rather than the extended, fingers are the ones counted. (2/8)

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 (!).

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/

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)

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.

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) nature.com/articles/srep1…

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) vox.com/2014/7/15/5881…

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)