Why do mangoes have monstrous seeds?

Also why obesity is not your fault, how bacteria might contribute to arthritis, and exposing the myth of the young brain

Dec 07, 2022

Hello! How have you been?

I’ve been super-busy with *checks calendar to see that there are no World Cup matches today*… work. ;)

It certainly has been an interesting World Cup. Well, at least the group stages were. Now, we’ve got the usual suspects heading to the Quarterfinals. And Morocco. So, go Morocco! Tagines for all.

It’s a funny thing, the beautiful game. You ask me what I ate for lunch yesterday and I don’t remember. But I remember goals from every match from Italia ‘90 and every World Cup since.

I could go on, but this is not a sports-themed newsletter and hottakes on sports like tagines are best served hot (hence the name “hottake”). I’ve been posting more of those as well as other musings for the past month on mastodon. And I have to admit that it’s been quite nice.

Mastodon is like Istanbul. There’s an old-world charm and cats everywhere. And Twitter was, when I left it, like Manhattan in a disaster movie. I can only imagine what it’s been like with Godzilla both owning the place and running around with other recently reinstated radioactive monsters.

The real test of Mastodon for new users will be once the novelty wears off. So, far there has been plenty to talk about. I think if you put progressive, empathetic, science-trusting, social-justice-seeking people in one place they will always have interesting things to say. But since there’s no profit motive, we will have to see what the future holds. Corporate social media is deviously good at pushing people’s buttons because that’s how they make their money. They know that negative emotions are more likely to get people to react so they encourage fights in the name of “free speech”. They feed the constant news-cycle. They make you think that every reaction is worth broadcasting.

Jelani Cobb spelled out his own reasons for quitting Twitter in the New Yorker recently.

No matter which side prevails, the true victor in any war is the person selling weapons to both sides.

Bingo. In a casino the house always win. Or in Indian sports terms, not only can the petulant brat walk off with the cricket bat and ball whenever he feels like it, not only does he get to make and change the rules, but he wins every time you choose to play.

Anyway, the best thing said about Twitter was said on Twitter in a completely different context. :)

Tweet by Cookie Monster “Me no cry because cookie is finished. Me smile because cookie happened.”

Obesity is not your fault.

The past 30 years have produced an epidemic of obesity— mostly because evolution did not prepare us for so many calories and so little physical activity.

Dr. Louis Aronne, a leading authority on obesity, explains how a period of caloric excess can damage the neural connections that manage metabolism, throwing weight regulation out of whack.

This is a super podcast for anyone feeling shame for their weight. The science is on your side. It’s not your fault.

Does bacterial infection lead to arthritis?

In a new study in Science Translational Medicine, autoantibodies were detected in people at risk for rheumatoid arthritis before development of clinical disease. The source of these autoantibodies was not known before. But now it seems that a bacterial strain might be involved.

This is a wonderful study that adds to the recent recognition of the importance of microbes to nearly every aspect of human health.

Why do some fruits have large seeds?

The answer may surprise you.

No, really, it might. Some of the stuff I learned while writing this science column for Hindustan Times took me by surprise.

To us, seeds in fruits are a nuisance that get in the way of enjoyment. Think of the well-established breeding efforts that have led to the marvel of seedless bananas, grapes, and watermelons and you get the picture.

To plants, seeds are the whole point of fruits – a vital means of dispersal to ensure that they can spread widely instead of crowding in the same area.

File:Mangifera indica pit.jpg - Wikipedia

A seedless fruit might be desirable in a supermarket, but it is defective for plants that put in so much energy into creating a desirable fruit: the plant gets nothing in return. They are, instead, left with a dead end for their survival.

A much more favorable outcome for plants is that animals consume their fruits and discard seeds or that seeds pass through animal digestive tracts and come out intact on the other end. Under favorable conditions, these seeds can germinate to continue the cycle of life.
Nature is replete with many examples of fruits that spread this way. Chili peppers, for example, are swallowed by birds and their intact seeds are dispersed in excrement. Birds are not deterred by the spiciness of chili peppers because they can’t taste capsaicin; instead, spiciness from capsaicin is meant to stop mammals from chewing on chili peppers (though it didn’t work for those humans who developed a preference for the heat).
All of this makes sense for fruits that have small seeds, but what about fruits like mangoes that have large and hard seeds? Humans and monkeys enjoy these fruits and eat them, tossing aside seeds. But which gigantic animals could have possibly swallowed mango seeds in the past?
The answer is – large herbivores like elephants and rhinos. By looking at dung piles of African forest elephants, researchers recently found that these large mammals which can swallow fruits whole had been important for dispersal of fruits in the past. Because elephant digestion is slow, large seeds are found in dung many kilometers away, providing new areas for spread of fruit trees.
Several researchers have also found that Asian elephants can swallow mangoes whole. And this might have contributed to the evolution and spread of the fruit in the past. Of course, now elephant populations have undergone a precipitous decline.

So what happens if the animal that helped to spread a fruit with a large fruit becomes extinct?

There are a number of fruits from subtropical America (such as the avocado) that have large seeds. But there are no native, large animals that could eat them whole and spread their seeds.

Scientists think that fruits such as avocados are relics from a different time.

Ground Sloth - White Sands National Park (U.S. National Park Service)

Over 13,000 years ago there were large mammals such as giant ground sloths, elephant-like gomphotheres, and mammoths in the western hemisphere. Avocado plants probably depended on large animals eating fruits whole and defecating seeds for their spread.