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Holding breath and avoiding inhaling dust and flies possibly doesn't require as fine motor control as necessary for speech. In that light, the first paragraph o

by rndn 11y ago

Holding breath and avoiding inhaling dust and flies possibly doesn't require as fine motor control as necessary for speech. In that light, the first paragraph of your comment can't refute the hypothesis without referencing some empirical results, so the second paragraph is absurdly confident.

sandworm101 11y ago
I would argue that keeping things out of our airways is a little more advanced than just holding one's breath. Coughing up junk or dealing with water/swimming are common to mammals. Even swallowing requires coordination of the various parts beyond simply not breathing. I read a few years ago about a machine to allow paralyzed/comatose people to cough properly as this hugely reduces throat infections.
- jschwartzi 11y ago
  Yeah, people tend to underestimate how complex the respiratory tract is. Cough assist is basically just a machine that holds an insufflation pressure and an exsufflation pressure for specific times to emulate a cough. Independently of the servo programming they're less complicated than speech.
joeyo 11y ago
Dead on. There is very likely some very specialized neural motor control circuitry that humans use for speech that is missing from other primates. If you consider, for example, dexterous finger movements, there is a strong correlation between the number of direct corticospinal [1] projections and degree of finger dexterity that the species exhibits. Rodents and many other mammals have no projections at all. Monkeys have some; humans have many [2, see fig 1]. So which primates have corticospinal projections for their vocal cords? Okay, that's actually a trick question because the vocal cords are innervated via cranial nerves emanating from the medulla [3], rather than via spinal cord. However, in humans, there are direct monosynaptic projections from cortex to these medullary motor neurons. These projections do not exist in macaques (and presumably not in other monkeys) or in chimpanzees [4, see fig 2]. I'm not sure if it's known whether gorillas or orangutans have them. 1. https://en.wikipedia.org/wiki/Pyramidal_tracts#Corticospinal_tract 2. http://www.nature.com/nm/journal/v13/n5/full/nm1595.html 3. https://en.wikipedia.org/wiki/Nucleus_ambiguus 4. http://www.sciencedirect.com/science/article/pii/S095943881400107X

by rndn 11y ago

sandworm101 11y ago

I would argue that keeping things out of our airways is a little more advanced than just holding one's breath. Coughing up junk or dealing with water/swimming are common to mammals. Even swallowing requires coordination of the various parts beyond simply not breathing. I read a few years ago about a machine to allow paralyzed/comatose people to cough properly as this hugely reduces throat infections.

jschwartzi 11y ago
Yeah, people tend to underestimate how complex the respiratory tract is. Cough assist is basically just a machine that holds an insufflation pressure and an exsufflation pressure for specific times to emulate a cough. Independently of the servo programming they're less complicated than speech.

joeyo 11y ago

Dead on. There is very likely some very specialized neural motor control circuitry that humans use for speech that is missing from other primates. If you consider, for example, dexterous finger movements, there is a strong correlation between the number of direct corticospinal [1] projections and degree of finger dexterity that the species exhibits. Rodents and many other mammals have no projections at all. Monkeys have some; humans have many [2, see fig 1]. So which primates have corticospinal projections for their vocal cords? Okay, that's actually a trick question because the vocal cords are innervated via cranial nerves emanating from the medulla [3], rather than via spinal cord. However, in humans, there are direct monosynaptic projections from cortex to these medullary motor neurons. These projections do not exist in macaques (and presumably not in other monkeys) or in chimpanzees [4, see fig 2]. I'm not sure if it's known whether gorillas or orangutans have them. 1. https://en.wikipedia.org/wiki/Pyramidal_tracts#Corticospinal_tract 2. http://www.nature.com/nm/journal/v13/n5/full/nm1595.html 3. https://en.wikipedia.org/wiki/Nucleus_ambiguus 4. http://www.sciencedirect.com/science/article/pii/S095943881400107X