Neoteny

Neoteny, also called juvenilization, is when animals slow down their physical growth. This means some animals keep traits from when they were young, even after they become adults. For example, some animals may stay small or have smooth skin like they did when they were babies.

In modern humans, neoteny is more noticeable than in other primates. This means humans often look more like children compared to other similar animals when they grow up.

Neoteny is important for studying how animals change over time and how they adapt. It helps scientists understand evolution and how animals, including pets, develop certain traits. This idea connects to larger topics like how animals change during their growth and development.

History and etymology

Julius Kollmann created the term "neoteny" in 1885 after studying the axolotl, an animal that stays in a tadpole-like stage with gills, unlike other adult amphibians such as frogs.

The word "neoteny" comes from German. Kollmann made it from Greek words meaning "young" and "to stretch". In 1926, Louis Bolk described neoteny as an important part of what makes humans unique. Later, Stephen Jay Gould wrote about Bolk’s ideas in his book Ontogeny and Phylogeny.

In humans

Neoteny in humans means that our bodies grow more slowly than in other primates. This slower growth gives humans special features like larger heads, flatter faces, and shorter arms. These changes might have happened because people liked partners with youthful looks over time. Because of this slower development, humans could learn better ways to share feelings and emotions. Some scientists think this slower growth was very important in how humans evolved and changed over many years.

In domestic animals

Further information: Domestication of animals

Neoteny is often seen in animals that people keep as pets, like dogs and mice. This happens because these animals have more food and fewer challenges. With less need to compete, they can grow and have babies sooner than animals in the wild. The way we care for these animals also affects whether they show neoteny.

When people began keeping dogs not just for work but as friends, they chose dogs with certain looks that reminded them of puppies. These traits, like short noses and big eyes, are often found in young puppies, and people find them very appealing. Some dog breeds, such as the Komondor, Saint Bernard, and Maremma Sheepdog, show these puppy-like features more strongly. The Cavalier King Charles spaniels are a good example, with their large eyes and floppy ears that make them look like young dogs even as adults.

Studies looking at the skulls of wolves and many dog breeds have found that while some dog skulls look similar to young wolves, most dogs do not show this same pattern.

In other animals

Neoteny, or juvenilization, is when an animal keeps its young traits longer than usual. This happens in many animals. For example, some frogs and salamanders stay in their young form longer. Insects, like certain types of aphids, can also show neoteny. This often happens in cold places where growing larger uses too much energy. Some insects never grow wings if they don’t need to move far.

Subcellular neoteny

Neoteny is usually talked about in animals, but it can also happen inside cells. Scientists have noticed this in tiny parts of cells, called organelles.

One example is in sperm cells. In these cells, a special part called a centriole looks younger than it should. In fruit flies, one of the centrioles in their sperm keeps a simpler, younger shape. This is called the Proximal Centriole-Like.

Normally, centrioles grow step by step. But in this case, they stay in an earlier stage, showing neoteny at the cellular level.

Main article: Proximal Centriole-Like