What would be needed to function with a third arm or eye?

Factual Questions
1

Since the brain is made up of two halves, would the brain need to evolve into 3 sections to support a third arm or a third eye? I’ve always wondered what it would be like to have an eye on the back of my head or an arm that could scratch my back, but it seems that since the human body is symmetrical that everything would have to evolve to support this.

2

Well, some might say so, but we in fact have four limbs, which are independently controlled;

we also have a mobile jaw/tongue arrangement, which is capable of chewing gum while we are walking;
we do not have a separate brain hemisphere for each of our independently moving parts, so it seems likely to me that a third leg/arm could be accomodated.

After all, spiders have eight, squid ten.
Given a few hundred years of genetic engineering humans will be able to have any number of independently operating appendages…
if you can still call them humans at that point.

SF worldbuilding at
http://www.orionsarm.com/main.html

3

I think we have the capacity to integrate an extra component or two.

I’ve always wanted a third arm like the “Moties” have.

4

Four arms would be ideal for hand soldering: one hand for the soldering iron, one for the component, one for the solder, and one for the circuit board. :slight_smile:

5

Yeah, but just where would you put the other two arms? Either you’d need a seriously complicated shoulder joint, or to put them somewhere else, where they’d be less useful.

Me, I want a prehensile tail. That’d be sweet.

6

If a bloody MONKEY can do it, you bet I can do it too… on second thought I´d rather not have that brain implant, I can live with an itch on my back. :smiley:

7

There was an early VR experiment, where the subject was a lobster, with extra limbs. They were controlled by shoulder and hip movements. With a little practice, the subjects got surprisingly good at manipulating them.

Um… No cite available… Something I read in Discover Magazine, maybe five years ago…

Trinopus

8

I remember reading that, too, Trinopus, so either we’re having a mutual false memory or it really did appear in Discover.