Sixty percent of adults can't digest milk - USATODAY.com

Sixty percent of adults can't digest milk - USATODAY.com

SAN FRANCISCO - Got milk? If you do, take a moment to ponder the true oddness of being able to drink milk after you're a baby.

No other species but humans can. And most humans can't either.

The long lists of food allergies some people claim to have can make it seem as if they're just finicky eaters trying to rationalize likes and dislikes. Not so. Eggs, peanuts, tree nuts, fish, shellfish soy and gluten all can wreak havoc on the immune system of allergic individuals, even causing a deadly reaction called anaphylaxis.

But those allergic reactions are relatively rare, affecting an estimated 4% of adults.

Milk's different.

First off, it's not actually an allergy in that there's not an immune response.

People who are lactose intolerant can't digest the main sugar —lactose— found in milk. In normal humans, the enzyme that does so —lactase— stops being produced when the person is between two and five years old. The undigested sugars end up in the colon, where they begin to ferment, producing gas that can cause cramping, bloating, nausea, flatulence and diarrhea.

If you're American or European it's hard to realize this, but being able to digest milk as an adult is one weird genetic adaptation.

It's not normal. Somewhat less than 40% of people in the world retain the ability to digest lactose after childhood. The numbers are often given as close to 0% of Native Americans, 5% of Asians, 25% of African and Caribbean peoples, 50% of Mediterranean peoples and 90% of northern Europeans. Sweden has one of the world's highest percentages of lactase tolerant people.

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Memes: Replace Genes as Engine driving Human Evolution

The idea of memes as a cultural analogue of genes has been much maligned, and most biologists still reject it. Yet memetics has much to offer in explaining human nature.

MemeTheory
According to meme theory, humans are radically different from all other species because we alone are meme machines.

Human intelligence is not just a bit more or a bit better than other kinds of intelligence, it is something completely different, based on a new evolutionary process and a new kind of information.

Differentiating
The main difference between conventional theories and memetics is this: most biologists assume that culture and language evolved because they helped humans survive and pass on their genes, and that genes retain ultimate control.

Memetics challenges that assumption. Although the capacity for imitation must once have been adaptive for the apes who started it, evolution has no foresight and could not have predicted the consequences of letting loose a new evolutionary process. Nor could it have retained control of memes once they began evolving in their own right.

Proliferation
So memes began to proliferate. What began as an adaptation soon became like a parasite - a new evolving entity that changed the apes and their world forever. Once memes were proliferating, individuals benefited from copying the latest and most successful ones, and then passed on any genes that helped them do so.

Memetic Drive
This "memetic drive" forced their brains to get bigger and bigger, and to become adept at copying the most successful memes, eventually leading to language, art, music, ritual and religion - the successful designs of human culture.

Clickety Click here for the full Article from New Scientist