Evolution of the human brain

  • #101
Chronos
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All of evolution is survival driven. Traits that do not advance survival are doomed to extinction. The major advantage of human intelligence was the ability to economize efforts. Chasing a herd of bison off a cliff was far more efficient [not to mention safer] than singling out one to pelt with sticks and stones. Erecting a portable shelter was more expedient than competing for local cave space. This is the evolutionary advantage of intelligence - recognizing ways to increase the pay value of survival related tasks. It is an adaptable approach.
 
  • #102
Simon Bridge
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Traits that do not advance survival are doomed to extinction.
For a given value of "enhance survival" ... i.e. the peacocks tail probably hinders survival - but it could be viewed as a side-effect of a favorable trait ... say, the ability to discriminate healthy plumage?

Not all traits enhance survival for all time - so we would expect, in any age, to find disadvantageous traits which are yet to die out.

Haven't we been over this ground before?
 
  • #103
Pythagorean
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Well, with Christmas over and nothing to do...

To try to summarive my current views on the subject:
1) The human brain has evolved mechanisms for spatial reasoning and pattern recognition, but is not born with the physical intuitions dicussed in the "Physics for Infants" article posted by Pythagorean (#40).
2) The physical intuitions come about by the interaction of the spatial reasoning and pattern recognition mechanisms with a world that obeys the laws of classical mechanics (i.e. via learning). This seems to be supported by some of the evidence posted by atyy suggesting that these intuitions develop over time (#69).

One reason I favor this model is by analogy to the way our visual processing circuitry develops. While it might make sense for the way our eyes are wired to the brain to be pre-determined by genetics, the wiring actually occurs in response to simulation of the eyes by the environment (as shown by the classic monocular deprivation experiments done by Hubel and Wiesel). Of course, certain genetic factors influence the process (for example, certain neurotrophic factors define a specific critical period during which the wiring can occur), but this is a nice example that clearly demonstrates how neural circuitry develops in response an individual's experiences.

Of course, this model essentially specifies the inevitable development of physical intuition because no infant will experience a world not governed by classical mechanics. So, in this sense, you can say physical intuitions are pre-determined. Of course, it would be interesting (but highly unethical) to test whether raising an infant in some virtual reality that presents different physical laws could alter the learned physical intuitions of the child or whether the infant still develops innate physical intuitions consistent with the real world. Perhaps such experiments might be possible using virutal reality systems for studying mice (for example http://www.nature.com/nature/journal/v461/n7266/full/nature08499.html).

I generally agree with you, but I still think the innate side is being (significantly) undersold. First of all, let me just say that I really appreciate your approach to discussion and I value your perspective; I know neuroscience is a huge diverse topic and different people know it at different scales and aspects (from molecular to cells to systems to behavior) and our introductory textbooks are always changing and always wrong somewhere.

I will start with monocular deprivation, since I find it relevant to the context. It helps demonstrate the false dichotomy of learned vs. innate. Then I will talk about the vestibular system and some of the innate wiring between visual and vestibular systems that lend to physical intuition.

Monocular Deprivation

While some of the wiring is a result of learning, that is really more at the level of engrams than over all wiring structure, and this is a functionally relevant distinction. In particular, it appears that invariant aspects of our environment (such as would be physics) are more innate, while variant aspects (shapes, colors, lighting) would be more learned. The literature:

“ The basic structure of cortical maps is therefore innate, but experience is essential for specific features of these maps, as well as for maintaining the responsiveness and selectivity of cortical neurons.”
The Role of Visual Experience in the Development of Columns in Cat Visual Cortex
http://www.sciencemag.org/content/279/5350/566.abstract?sid=45909110-de27-4bbf-bf1d-ce471a76064e

“We argue that these spontaneous patterns may be better understood as part of an “innate learning” strategy, which learns similarly on activity both before and during visual experience. With an abstraction of spontaneous activity models, we show how the visual system may be able to bootstrap an efficient code for its natural environment prior to external visual experience, and we continue the same refinement strategy upon natural experience.”

Innate Visual Learning through Spontaneous Activity Patterns
http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1000137

“A comparison of the layout of the two maps formed under these conditions showed them to be virtually identical. Considering that the two eyes never had common visual experience, this indicates that correlated visual input is not required for the alignment of orientation preference maps.”

Development of identical orientation maps for two eyes without common visual experience
http://www.nature.com/nature/journal/v379/n6562/abs/379251a0.html

“This suggests that the initial development and layout of orientation preference maps are determined by intrinsic processes that are independent of visual experience.”
Development of orientation preference maps in area 18 of kitten visual cortex.
http://www.ncbi.nlm.nih.gov/pubmed/9283830

“Previous experiments indicate that the shape of maps of preferred orientation in the primary visual cortex does not depend on visual experience. We propose a network model that demonstrates that the orientation and direction selectivity of individual units and the structure of the corresponding angle maps could emerge from local recurrent connections.”
Intracortical origin of visual maps
http://www.nature.com/neuro/journal/v4/n4/full/nn0401_431.html

Further evidence shows rescue and prevention of monocular deprivation, implying that the negative effects of monocular deprivation are a result of expected inputs. The system is expecting inputs that have spatial structures consistent with our physical world and when you block light input, the system begins making correlations on intrinsic noise. The evidence of prevention and rescue:

http://europepmc.org/abstract/MED/9987024
http://www.nature.com/nature/journal/v378/n6553/abs/378189a0.html
http://www.pnas.org/content/103/22/8517.short

Additionally, horses can walk the same day they are born without running into walls, so while being born earlier in our developmental period has in increased effect on outcome from learning for us and cats, it shouldn’t diminish the innate hierarchy of the circuits and how they connect to sensory organs before learning takes place (or while learning takes place in the case of early birthers like humans).

What’s neat about the visual system… is it has an intrinsic orientation for down, thought to be based on the vestibular system’s graviception.

“it has been suggested that the cortical vestibular network is involved in the perception of our spatial orientation relative to the gravitational vertical (17, 24, 25,27).”
Representation of Visual Gravitational Motion in the Human Vestibular Cortex
http://www.sciencemag.org/content/308/5720/416.abstract?sid=a51c9b39-95e3-48d4-9765-adcb7f2622df.

Vestibular System

Consider how learned and innate are coupled through overall wiring architecture vs. local synaptic connections when considering how vestibular, visual, motor systems, and hippocampus all talk to each other to form fine connections in the first place.

The vestibular system and it’s wiring with respect to the visual system are a conserved trait (across many, if not most, vertebrates). The vestibular system is essentially an acceleration detector. It can detect:

1) Angular acceleration (through the semicircular canals)
2) Linear acceleration (through the utricle, for horizontal movement and the saccule for vertical movement)
3) Gravity (also otolithic organ)

So we’ve basically evolved a little Newtonian experimental lab inside of brains that can confer to us the laws of motion. Gravisensors have particularly interesting implications in our innate sense of gravity and is believed to be coupled to our visual system (as described above). Another well-known innate coupling between visual and vestibular systems is the vestibular-occular reflex which compensates head movements with eye movements.

Interestingly:

"According to Einstein's equivalence principle, linear accelerations experienced during translational motion are physically indistinguishable from changes in orientation relative to gravity experienced during tilting movements. Nevertheless, despite these ambiguous sensory cues provided by the primary otolith afferents, perceptual and motor responses discriminate between gravity and translational acceleration. "

http://www.ncbi.nlm.nih.gov/pubmed/11710454



a note

Many of the fundamental assumptions of classical physics are "wrong" (or only true "in the limit" if you like). Not surprisingly, these limits are at the scales of our senses whereas the conflicting modern concepts are outside of them. Properties of the classical realm are much closer to our intuition than reality. These include continuity, locality, solidity, etc. Our intuition for the physical world underlies classical physics. We impose our perception and intuition for the world on the discipline of physics. And this is exactly the reason why classical physics is "wrong": because our sensory systems measure things on a limited scale of reality: the classical scale. And our brain has already been wired in an appropriate hierarchy to interpret those signals successfully by the time we start learning the finer details of our environment.
 
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  • #104
Chronos
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For a given value of "enhance survival" ... i.e. the peacocks tail probably hinders survival - but it could be viewed as a side-effect of a favorable trait ... say, the ability to discriminate healthy plumage?

Not all traits enhance survival for all time - so we would expect, in any age, to find disadvantageous traits which are yet to die out.

Haven't we been over this ground before?
I agree, but, many traits have hidden survival value; like peacock plumage. That only suggests peacocks have found a special niche within their survival strategy. It also suggests they have discovered a way to preserve their genes. Every species adjusts to find a way to promote characteristics that are attractive to the opposite sex. Evolutionary history strongly suggests that is the case for every species. That is not necessarily important to the long term survival of the species, but, has short term advantages. Long term survival requires short term experimentation.
 
  • #105
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The Lawrence Krauss video from post #12 is fairly typical pop science - i.e. it is more about entertainment than education. Still: Krauss could have been a bit more careful to spell out what we mean by "purpose" in adaptations. He's just being glib - cavemen did not have to solve Schrodinger's equation or do triple integration by parts. All he means is that we are using traits that came into existence under other influences to help us understand quantum mechanics. The process neatly explains why we can understand QM at all as well as why QM is counter-intuitive.
Yes, it's a pop (informal: for the layman) video but it's not for entertainment purposes.

I've looked at other quotes from Krauss and the picture forms of a man working toward de-institutionalizing people who don't understand how anyone can survive outside the framework of religion. The video isn't about QM vs Classical, nor is it about evolution. All that preliminary stuff is just a jerry-built set up for "...Nature seems strange and at times almost unfathomable..." leading to, "If reality seems strange, that's OK!" He goes on to, "The searching is often more profound than the finding. It's the searching for answers through life, in some sense, that makes life worth living. If we had all the answers we could just sit back and stare at our navels."

Translation/paraphrase: 'It's perfectly possible to do well, and even thrive, outside the institution where all the rules are laid out and all the answers given (religion). In fact, that is what we do out here most of the time, search for the answers, and we have a great time doing it!'

Krauss is a pal of Dawkins and I suspect the inspiration for this sort of 'social work' arose from discussions with him. I've seen Dawkins team up with Derren Brown in the past to do similar work on religious people. They both target mystical thinking of any kind, independently and as a team. Krauss' tack is a lot more enlightened than just battering the religious with citations of the logical fallacies they're making, but I'm still skeptical of its long term efficacy. But my point is the video's actually not intended as entertainment. He's got an agenda. He's an unmarked religious deprogrammer.

So, you and atty are right to characterize it as something that shouldn't be taken seriously as a biology lesson. He has a different goal in mind and, that being the case, he got sloppy with the biology/evolution part. His actual goal, however, is more serious than entertainment.

On the question of whether or not this is the right video:

Lawrence Krauss says that
We evolved as human beings a few million years ago on the Savanna in Africa and we evolved to escape tigers, or lions, or predators. You know, how to throw a rock or a spear or how to find a cave and we didn't evolve to understand quantum mechanics.
Notice that arnshanker is quoting Krauss verbatim from the video I posted. I can't explain the absence of quotation marks or italics, but I'm completely satisfied he's referring to this video.
 
  • #106
atyy
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Wow, zoobyshoe, surely it's not so insidious. He's just explaining why he doesn't understand quantum mechanics, while the rest of us do.
 
  • #107
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Wow, zoobyshoe, surely it's not so insidious. He's just explaining why he doesn't understand quantum mechanics, while the rest of us do.
“Every atom in your body came from a star that exploded. And, the atoms in your left hand probably came from a different star than your right hand. It really is the most poetic thing I know about physics: You are all stardust. You couldn’t be here if stars hadn’t exploded, because the elements - the carbon, nitrogen, oxygen, iron, all the things that matter for evolution and for life - weren’t created at the beginning of time. They were created in the nuclear furnaces of stars, and the only way for them to get into your body is if those stars were kind enough to explode. So, forget Jesus. The stars died so that you could be here today.”
― Lawrence M. Krauss
http://www.goodreads.com/author/quotes/1410.Lawrence_M_Krauss
 
  • #108
atyy
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I should have put a smiley on my previous post ...
 
  • #109
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I should have put a smiley on my previous post ...
:rofl:
 
  • #110
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I should have put a smiley on my previous post ...
Forget smilies, stars dies so you could joke here today.
 
  • #111
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Truth be told, I haven't read this entire thread, but here is another take on the evolution of the human brain that many scientists don't even know about (shameless plug for my field of study hehehe).

Sialic acids are a family of very special 9 carbon sugars that cap the end of glycan structures on cellular surfaces. The most common form of sialic acid (which I'll call NeuNAc from now on) in humans is the molecule depicted below:

1456161921121780.png


Animals other than humans OTOH, are capable of producing a hydroxylated form of NeuNAc called Neu5Gc (as shown below):

neu5gc1.jpg


Many, many moons ago, humans developed a mutation in their CMAH gene (enzyme that is responsible for hydroxylation of NeuNAc), which caused humans to no longer to be able to produce Neu5Gc. In otherwords, another thing that makes us uniquely human on a molecular level is our over abundance of NeuNAc and no production of its hydroxylated form.

Ok so what? Well, outside of DNA, sialic acids have been called the most interesting molecules known to man and for good reason. Polysialic acids (PSA) is a weird post-translational modification found within the synapses of neurons on proteins called neuron cellular adhesion molecules (NCAM) (Polysialic acid is just what it sounds like--a polymer of NeuNAc). When PSA is present on NCAMs, it behaves as sort of a hydrogel that acts as a sort of anti-adhesive. It doesn't take much of a jump to see how this could be extremely important for things like neural plasticity, learning, memory, and brain development. Sialic acids are extremely important for brain function and development and are tightly regulated.

It is believed that CMAH mutated around 2.8 mya, before the human brain began developing in our ancestors 2.1-2.2 mya. Neu5Gc is specifically regulated during development in non-human animals and is tissue specific. While, Neu5Gc is found ubiquitously in adult chimp organs, Neu5Gc is specifically down regulated in the brain of chimps. So what would the effect be if you simply took away Neu5Gc expression all together (by say mutated CMAH)? Would the result be a human brain? Does this help us solve physics problems?

If this interests you, just look up Varki papers on Neu5Gc, which I don't currently have access to. He's the king of evolutionary glycobiology and explains this much better than I just did (not really my area of expertise).
 
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  • #112
atyy
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Here's another version of the quote, this time from Zurek, with a very interesting twist:
http://arxiv.org/abs/quant-ph/0306072
"There is, however, another reason for this focus on the classical that must have played a decisive role: Our senses did not evolve for the purpose of verifying quantum mechanics. Rather, they have developed in the process in which survival of the fittest played a central role. There is no evolutionary reason for perception when nothing can be gained from prediction. And, as the predictability sieve illustrates, only quantum states that are robust in spite of decoherence, and hence, effectively classical, have predictable consequences. Indeed, classical reality can be regarded as nearly synonymous with predictability.
 
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