Uh, the only thing really limiting our brain capacity is ourselves.

Interesting fact 1: The human brain has an average of 85 million non-neuronal cells, an average of 86 million neuronal cells, and an average of a quadrillion synaptic connections.

Interesting fact 2: It is fueled by the human metabolic rate, which averages in excess of a thousand kcal/day, kcal means a thousand calories, so a thousand of those means one million calories a day - absolute minimum. The more lean mass someone has versus fat, the higher this rate. The more physically active a person is, the higher this rate. The healthier a person eats, the higher this rate. People have been known to have metabolic rates in excess of 2 million calories a day. That's a lot of energy.

Interesting fact 3: The human brain's function is largely only limited by the individuals own desire to think.

Interesting fact 4: The currently most advanced computer processor on the market is, (of course) a graphics processor, and has exactly 6 million transistors, which would be like a cell in the human brain. 1024 Shader Processors, capable of 8 single precision operations per clock per SP, or 8192; 128 Special Function Units, capable of 4 special function operations per clock per SFU, or 512; and 6144 Texture Filtering Units, which do fairly complex operations, but only one per unit per clock; adding up all those numbers nets just shy of 15 thousand operations per clock. You could equate these with synaptic connections... That wouldn't be precise, but it serves the comparison.

Interesting fact 5: The above processor is fueled by a clock rate, which for this particular processor is 607 Mhz at the core - 607 million hertz, 1215 Mhz at the shader - 1.2 billion hertz, and 3414 Mhz at the memory bus - 3.4 billion hertz. Now, the math to determine from here the rate at which instruction and information can flow is much much more complex than I'm going to bother going into, but a REASONABLE estimate would be about 2 billion hertz. This might seem a lot more than our brain, but...

Interesting fact 6: 1.2 million times a quadrillion, 2 billion times 15 thousand. Which do you think is a bigger number?

Interesting fact 7: A graphics processor is limited to working only on one type of thing: rendering an animated sequence of images.

NOTE: This is by no means an exact performance analysis of the human brain vs this particular graphics processor, it's merely a rough comparison. Very rough. So rough that my fellow super geeks would probably tear me to shreds and gobble me up whole as I watch helplessly just for even putting such a half-arsed comparison online.

Someone once said that the human brain is the most complex computer processor in the known universe. This was true then, it's still true today, and it'll likely remain true for at least a very long time if not until we go extinct somehow. We're still evolving, our brains are more complex today than they were just a thousand years ago.

I can without a doubt tell you that there are people out there capable of feats of illogical mental prowess such that no computer will ever achieve, being, by nature, purely logical beasts. Human intuition, by nature, a purely illogical mental function, is actually our greatest mental gift, it's what allows us our sentience in the first place! Logic machines will never be sentient. Until and unless someone can manage to logically program illogic, robots will never achieve sentience. Either that or someone can manage to design an illogical system from the ground up...... Slightly more likely than using a logic system to program illogic. Marginally... Don't get your collective panties in a bunch, science fiction fans... It IS possible - but unlikely.

As for being a primitive species... That'd be a misnomer, as far as genetics and speciation goes, we're the most advanced species currently known. We ARE a primitive SOCIETY, though. That will lrtfalavltinuwges (likely remain true ... extinct somehow) as well.

EDIT: lost count of my count. lol. fixed.