Extra Gene Drove Instant Leap in Human Brain Evolution

[entelecheia]

The researchers don't think SRGAP2 is solely responsible for that brain expansion, but the genetic interference does have potential benefits. Polleux and colleagues mimic the function of the human-specific SRGAP2 duplication in mice. They show that loss of SRGAP2 function accelerates neurons' migration in the developing brain, potentially helping them reach their final destination more efficiently. Moreover, neurons that have decreased SRGAP2 function, due to expression of the human-specific SRGAP2 display more knob-like extensions or spines on their surfaces, making the neurons appear much more like those found in the human brain. These spines enable connections between neurons to form.

http://www.sciencedaily.com/releases/2012/05/120503125804.htm

Which enviromental factors triggered these brain mutations? How extremely improbable are they that we cant mimic them in lab chimps?

 

[common_sense_seeker]

I didn't fully undertsand it but the article was interesting, especially the last two paragraphs imv

In addition to providing insight into the origins of the modern human brain, the findings offer clues to the neurodevelopmental disorders that humans are so prone to developing, including autism, epilepsy and schizophrenia, in which development of neuronal connections is affected. The researchers point to known cases of humans with structural brain defects and other symptoms that can be traced to disruption of the ancestral SRGAP2. They now intend to search for people carrying defects in the human-specific 'granddaughter' copy as well.

If this gene duplication did indeed produce an immediate effect during evolution as Eichler and Polleux suspect, they expect there must have been a fascinating period in human history characterized by "huge variation" in human cognition and behavior. SRGAP2 and other human-specific gene duplicates might also help to explain the big differences between humans and other primates, despite few apparent differences in our genome sequences.

"We may have been looking at the wrong types of mutations to explain human and great ape differences," Eichler says. "These episodic and large duplication events could have allowed for radical -- potentially earth-shattering -- changes in brain development and brain function."

 

[Write4U]

This may be of pertinent to your post. In any case it is an excellent article, complete with illustration.

Human Chromosome 2 is a fusion of two ancestral chromosomes

http://www.evolutionpages.com/chromosome_2.htm

 

[common_sense_seeker]

This may be of pertinent to your post. In any case it is an excellent article, complete with illustration.
http://www.evolutionpages.com/chromosome_2.htm

Hey, thanks! I didn't know this. The picture says it all. Definitely the merger of the two chromosomes.

 

[Aqueous Id]

Which enviromental factors triggered these brain mutations? How extremely improbable are they that we cant mimic them in lab chimps?

The mutation itself is probably random. The environment would play a role in selecting any trait that accompanies it. For example, suppose it increased eye-hand coordination. In conjunction with the evolution of the skeletal processes that enable erect posture, it would makes the use of the hands (freed from crawling) more critical to survival. Mutations affecting intelligence thereby contributed to the success of erect posterior and vice versa. I mention this since a manual task, chipping flint, is the definitive benchmark for intelligence. Obviously this engages a lot more brain function that eye-hand coordination. But insofar as the ability to chip flint leads to better nutrition, natural selection would leave more survivors to carry that trait into sexual maturity.

 

[Balerion]

The mutation itself is probably random. The environment would play a role in selecting any trait that accompanies it. For example, suppose it increased eye-hand coordination. In conjunction with the evolution of the skeletal processes that enable erect posture, it would makes the use of the hands (freed from crawling) more critical to survival. Mutations affecting intelligence thereby contributed to the success of erect posterior and vice versa. I mention this since a manual task, chipping flint, is the definitive benchmark for intelligence. Obviously this engages a lot more brain function that eye-hand coordination. But insofar as the ability to chip flint leads to better nutrition, natural selection would leave more survivors to carry that trait into sexual maturity.

Probably the last time a nerd got laid.

 

[Aqueous Id]

Not only that but his mate was more likely to have a full set of teeth

 

[Write4U]

Not only that but his mate was more likely to have a full set of teeth

Yes, in those days natural selection worked naturally. Today, it is man's very intelligence that determines the survival of other life on earth.

In 1992, Hurricane Andrew smashed an aquarium tank in Florida. About a half-dozen spiny, venomous lionfish washed into the Atlantic Ocean, spawning an invasion that could kill off local industry along with the native fish.

http://www.npr.org/templates/story/story.php?storyId=111695369

This may become a disaster of global proportions. Watch the video below. This is scary stuff.

Invasive Lionfish
The Issue
Video: Lions of the Deep

In less than a decade, the Indo-Pacific lionfish (Pterois miles and P. volitans) has become widely established along the Southeast U.S. and Caribbean. Lionfish are presently invading the Gulf of Mexico and South America. Recent estimates of lionfish densities indicate that lionfish have surpassed some native species with the highest estimates reporting over 1,000 lionfish per acre in some locations.

http://www.ccfhr.noaa.gov/stressors/lionfish.aspx

 

[wellwisher]

There is an area of biology called epigenetics, which is the study of changes in gene expression or cellular phenotype, caused by mechanisms other than changes in the underlying DNA sequence.

One thing that modern humans possess is will power. For example, our instinctive behavior is genetically coded in the DNA. The epigenetic changes, induced via will power, can modify the instinctive output one would expect from the DNA. This is a very flexible approach and does not require a new gene for each modification. For example, sexual desire is based on a certain DNA code. Epigenetics would explain the dozens of behavior variations that humans can think up and practice, until it appears natural, while still conserving natural instinct within the DNA; unconsciously. We can be close to apes on paper, but miles away at the same time.

 

[wellwisher]

Let me give an example. If we assume humans evolved from apes we would have been primarily vegetarians at the genetic level. But through epigenetic changes, due to the necessity of migration and an ice age, humans, through epigenetic changes, became omnivores so they could eat meat and other forms of food. The value of this is the underlying DNA is conserved while allowing experimental modifications that can adapt faster to changing conditions. There is always a stable genetic foundation to return tom if the conditions warrant it. Humans could survive nicely on only veggies, if the mind cooperated.