Of 37 phyla of multicellular animals, only six have evolved sight

From Life's Greatest Inventions from New Scientist.

The list of ten are:

1. Multicellularity

2. The eye

3. The brain

4. Language

5. Photosynthesis

6. Sex

7. Death

8. Parasitism

9. Superorganism

10. Symbiosis

All the essays are worth reading. A few observations from the essays.

Yet bigger and more complex isn’t necessarily better. As King points out, unicellular life still vastly outnumbers multicellular life in terms of both biomass and species numbers. “So you could say unicellular life is the most successful, but that multicellular life is the most beautiful and dramatic.”

[snip]

However, sight is not universal. Of 37 phyla of multicellular animals, only six have evolved it, so it might not look like such a great invention after all – until you stop to think. The six phyla that have vision (including our own, chordates, plus arthropods and molluscs) are the most abundant, widespread and successful animals on the planet.

[snip]

A nervous system allows two extremely useful things to happen: movement and memory. If you’re a plant and your food source disappears, that’s just tough. But if you have a nervous system that can control muscles, then you can actually move around and seek out food, sex and shelter.

[snip]

Armed with this, finding food would have been the top priority the earliest water-dwelling creatures. Organisms need to sort out nutritious from toxic food, and the brain helps them do that. Sure enough, look at any animal and you will find the brain is always near the mouth. In some of the most primitive invertebrates, the oesophagus actually passes right through the brain.

[snip]

The more complex functions of the human brain – social interaction, decision-making and empathy, for example – seem to have evolved from these basic systems controlling food intake. The sensations that control what we decide to eat became the intuitive decisions we call gut instincts. The most highly developed parts of the human frontal cortex that deal with decisions and social interactions are right next to the parts that control taste and smell and movements of the mouth, tongue and gut. There is a reason we kiss potential mates – it’s the most primitive way we know to check something out.

[snip]

In a sense, language is the last word in biological evolution. That’s because this particular evolutionary innovation allows those who possess it to move beyond the realms of the purely biological. With language, our ancestors were able to create their own environment – we now call it culture – and adapt to it without the need for genetic changes.