Apparently vertebrates diverged from crustaceans about the same time as octopuses. We have evolved a complex body with distributed functions, a closed circulation system, and high intelligence. So have octopuses.

Crustaceans have an ectoskeleton (hard shell) and no circulatory system. They are also universally dumber than a stone. At some point, the exoskeleton was jettisoned. We vertebrates went on to evolve our internal one, but the octopuses decided that no skeleton might work just as well.

It is often thought that vertebrates have a monopoly on both brains and the closed circulation system. However, the octopus and squid have come up with both of these. In fact, the octopus has got three separate hearts.

We can get a crude idea of brain power by counting neurons. The lobster has a mere 100,000. He is easily outstripped by the cockroach, with its million. That’s about as smart as those hard-shelled arthropods get. Here’s a list for us soft skinned creatures:

Animal	Neurons
Mouse	70 million
Rat	200 million
Octopus	300 million
Cat	700 million
Us	80 billion

That’s a fair amount of neurons for our octopus, so what does he do with this? In captivity, they exhibit very definite personalities: outgoing, shy, grumpy, etc. Furthermore, they like some people, and will play with them. Those they dislike will get squirted. They also use their big brains to escape from wherever their captors have installed them. If there is a way out, the octopus will find it.

The octopus has an excellent short and long term memory, and will remember people they have not seen in a while, either greeting them with open arms or again dousing them with a stream of water. They appear to be quite fickle.

The octopus will use tools. They will arrange rocks in front of their shelter and other similar tasks. They will figure out how to unlatch a box to get a treat. Interestingly, the octopus has to figure out all its tricks from scratch. Its parents die soon after it is born so there is no cultural or nurture learning.

One trick the octopus apparently retained from its crustacean ancestors: it can regrow a severed tentacle.

The octopus uses its three hearts in a similar fashion to us. We actually have two hearts, attached together. One pumps blood through the lungs and the other through the body. The octopus uses one for the body, and one each for its two gills.

There are a few other differences. A lot of our body control is in our head. In the octopus, there are extensive ‘smarts’ in the tentacles, and they will continue to function if severed, finding food and trying to lift it to where the mouth ‘ought’ to be.

They have four interesting defense mechanisms that we don’t. First, with no bones, they can squeeze themselves into improbably small crevices. Second, they are venomous (only one species is toxic to humans). Third, they can camouflage by changing skin color, and finally, they can squirt the famous cloud of black ink. Interestingly, we can make that same black ink, but we don’t squirt it, we use it to color our skin and hair.

They are missing one important vertebrate feature: the adaptive immune system. Let’s give them a couple of hundred million years and check back.

Who knows? By then they may be running the place. They are definitely brighter than any of our ancestors that were on the scene 200 million years ago.