In preschool or elementary school you probably remember learning about the basic tastes, out of which every complex taste is constructed. The four most commonly known ones are sweetness, sourness, saltiness, and bitterness. The fifth, umami (or savoriness) is lesser known in the West, and is best described as a meaty or brothy taste with long-lasting, mouthwatering sesation on the tongue. Umami describes the tastes of glutamates and ribonucleotides - think MSG (monosodium glutamate).

The mechanism of taste perception is fascinating. It starts with the taste buds located on your tongue, soft palate, esophagus, and epiglottis. You might also have learned in school that different parts of your tongue are responsible for different tastes (sweetness on the top, saltiness and sourness on the sides, and bitterness way in the back) - this is a myth and is based on a mistranslation of a 1901 German study. All the taste qualities are found in all areas of the tongue, though some regions are more sensitive than others.

The different types of taste buds are activated by the various components of your food dissolved in your saliva, and these impulses travel up to your brainstem, where various structures control automatic eating-related behaviors like swallowing and salivation. The signals then travel up to the thalamus, the gateway structure to the cortex, and then fan out to higher-level primary gustatory cortex, which is responsible for the perception of taste. 

Finally, from the gustatory cortex, the signals travel back deeper into the brain, to limbic areas that associate the tastes with emotions, reward, and memories.

Now think about this in the context of an unborn baby. A fetus' tastebuds begin to mature in the second trimester of pregnancy, and she will begin her first automatic sucking and swallowing behaviors around this time as well, providing vital neural stimulation for the process of the taste buds becoming wired up to taste circuitry in the brain. 

The brainstem matures early, allowing the fetus to automatically salivate in response to sweets or protrude her tongue to expel bitter liquids. This happens even though her cortex hasn't finished developing yet, meaning she can't yet perceive the actual tastes.

By the third trimester, almost all of the taste circuitry has finished maturing, and the fetus will begin to develop lifelong taste preferences based on the eating habits of her mother. This also happens in rats, where studies have shown that if expecting mothers are fed high amounts of distinctive-tasting fluids like apple juice, their pups will show enhanced preference for the same taste.

Sure, innate preference for tastes is part of the story, but there is surprising potential for taste preferences resulting from what the fetus experienced in the womb. In fact, if a pregnant mother eats a wide variety of foods, exposing the fetus to many different tastes through the amniotic fluid, her baby will typically show increased acceptance of novel foods.

Expecting mothers, arm yourselves with this knowledge and give your child a leading edge and lifelong advantage over picky eaters who can’t eat as healthy!

Humans take a long time to start walking

The onset of walking is thought to represent a critical milestone in development of the nervous system, when neuronal systems mature enough to coordinate the complex movements of multiple limbs and prevent the animal from falling over. How long it takes for babies to start walking is one area that scientists originally thought that humans differ from other mammals.

A human baby only starts to walk on shaky legs around a year after birth, but a foal can get up almost immediately and rodents like mice only require a few hours to start moving around. In a new study published in PNAS, a group from Lund University in Sweden has found why this difference exists – and surprisingly, it’s not because humans are uniquely different.

Most mammals start walking around the same developmental time!

They showed that human babies actually start walking at the same brain developmental stage as most other mammals that walk. If you look at progression of brain development after conception, and not birth, humans start walking at the same relative point in time.

This shows that the neural mechanisms that underlie the ability to walk are very similar across animals and the neural building blocks of human brains come together in a similar manner as even lower mammals that diverged in evolution many millions of years ago.

Analyzing brain development data from other animals allowed them to predict quite accurately when humans would start to walk. Though humans may be different in many ways, motor development of the brain is not one of them.

These findings shed new light on how developmental paths in early life could have been conserved evolutionarily from lower organisms all the way up to humans, and they lead to better understanding of the developmental clock and what events occur at what stage of development, which may have relevance for treating developmental disorders in the future.