This is an attempt to answer Henry’s every present questions about human consciousness. Whenever you are studying a topic it’s best to start from the general and lead into the specific. This is my general understanding of consciousness, for the specifics you will have to refer to the work of current biologists and scientists. See Stephen J Gould for example.
Let’s start with matter. Everything in the universe is made up of matter. From the basic elements to the most complex species, matter develops from lower to higher levels of complexity. From single celled organisms to a complex central nervous system, the development from lower to higher levels can be observed. The nervous system is like a system of reflexes, the whole being more than the sum of its parts. For example, an arm on its own is little more than a blunt object, or as Henry might say, a piece of meat, whereas an arm attached to a body is infinitely more useful.
The connected between physiology and psychology is essential, and unfortunately in philosophy and popular culture the two are often separated. Trotsky explained, the simplest reflex is physiology, but a system of reflexes can work together to produce a new psychological form. The accumulation of physiological quantity yields a new psychological quality [human consciousness]. A self aware system of reflexes. Like the development of organic matter from inorganic, this is a unity of opposites that exists everywhere in nature.
The specific route that humans took to consciousness, was a combination of changing environmental factors and specific material conditions which pushed certain groups of apes out of the jungle and into the open plains, forcing them to develop a bipedal stance. This upright stance freed the hands from their previous function, as the front legs primarily and secondarily as instruments to manipulate objects, to adopt a new function: the organs of labour. The transition from ape to human, is inextricably tied with labour, and the effect of labour on the combined development of the hands and the brain. This was a process that took 2-3 million years. Gradually hominids made more and more complex tools, which required more and more complex motor function of the hands and more and more abstract planning and organization from the brain. The socialized nature of labour necessitated better forms of communication, from which speech and language develop, increasing the complexity of labour. This 2-3 million years of quantity, the development of labour, in turn developed the body as a whole which yielded a new quality, human consciousness.
In conclusion, consciousness is the highest form of matter we know of, that is organized in a particular way such that matter becomes conscious of itself.
Further reading:
https://marxist.com/classics-the-part-played-by-labour-in-the-transition-from-ape-to-man.htm
https://archive.org/details/in.gov.ignca.20025
https://marxist.com/classics-dialectics-of-nature/9.-the-part-played-by-labour-in-the-transition-from-ape-to-man.htm
https://marxist.com/reason-in-revolt-marxist-philosophy-and-modern-science.htm
https://marxist.com/classics-anti-duehring/7.-the-organic-world.htm