By Keith Hayward
In this article, Keith explains in simple terms how life got going from complex carbon molecules and how life comes from non-life (a process called abiogenesis). He also claims that neuronal machines are a type of life which he predicts will carry on when humans have gone extinct. Keith is a member of Farnham Humanists committee. He is a retired motor engineer and he currently runs a retail garden nursery in Bisley, Surrey.
Introduction
In this article, the term “life” includes biological life and what I call machine life. The creation of life relies on a succession of stages, beginning with the formation of the universe. The widely accepted theory is that the universe was created some 13.8 billion years ago in a process colloquially known as the “Big Bang”. After its initial expansion, the universe cooled sufficiently – in just a fraction of a second – to allow the formation of subatomic particles. Scientists currently accept the existence of 17 types of subatomic particle. Together, these are known as the “Standard Model of Elementary Particles”, as shown in the figure below.
Why the Big Bang should have produced these 17 types of particle is not known, but these particles have the potential within themselves to enable the creation of everything within the universe that can be created, including all living matter and all machine matter.
This process began with quarks and gluons combining to form protons and neutrons. The protons and neutrons then combined in various proportions to create atomic nuclei. These nuclei combined with electrons to create atoms.
Initially, the Big Bang created mostly hydrogen atoms (symbol H, atomic Number 1), a little helium (symbol He, Atomic Number 2), and a tiny amount of lithium (symbol Li, Atomic number 3). Not much chemistry can be done with just hydrogen, helium and lithium! But these elements have mass, and mass causes gravitational attraction, which brought the clouds of hydrogen, helium and lithium together to form stars. As stars grew they started to produce nuclear fusion within themselves. Within this hot and dense environment, the conditions created heavier elements by the process of nuclear synthesis. By this method the stars created new elements up to iron (symbol Fe, Atomic Number 56 ). As stars exploded or disintegrated these elements were distributed around the universe.
But on planet Earth there are 94 naturally occurring chemical elements. The elements heavier than iron have been produced by the hotter and more dense conditions inside supernovae. The full list of known chemical elements is shown in the Periodic Table below. With the 94 native chemical elements plus several created by humanity there is scope for lots of chemistry.
The creation of biological life
Within this list of chemical elements, there exists one element that is of special importance in the chemistry of biological living things. This is carbon, (symbol C, Atomic Number 6). Carbon has the special property of being able to form a vast number of organic compounds with elements including hydrogen, oxygen and nitrogen, and the unique property of being able to create a near infinity of different organic chemical molecules. For example, every animal that has ever existed has had a DNA molecule that is unique to that particular animal. Carbon organic molecules can be extremely big, comprising thousands of atoms.
Carbon is the essential component of all biological living things on Earth. Without the existence of carbon with these special properties there could be no abiogenesis, and hence no intelligent life. These exceptional properties of carbon provide yet another example of as yet unexplained happenings in the progression towards the existence of biological life.
So how and when was biological life on Earth created? Palaeontologists are reasonably confident of the timescale – it occurred around 4,000,000,000 (four billion) years ago. But there is no comprehensive and detailed scientific hypothesis regarding abiogenesis – that is, the transition from non-living to living entities. Neither have scientists been able to recreate the vital steps in the artificial creation of life. A simple path for the stages of abiogenesis can be hypothesised as follows:
Prebiotic synthesis: It is known that there were many complex carbon molecules existing four billion years ago, both on the Earth and extra-terrestrially, including the monomers that are components of RNA and DNA: guanine, adenine, cytosine and thymine/uracil. There were also warm and chemically active environments such as shallow warm seas and around undersea thermal vents.
Membranes, which are essential for living cells: These form enclosed compartments that are separate from the external environment, thus providing the cell with functionally isolated spaces. The primary role of the lipid bilayer in biology is to separate aqueous compartments from their surroundings. Without some form of barrier delineating “self” from “non-self”, it is difficult to even define the concept of an organism or of life. This barrier takes the form of a lipid bilayer in all known life forms except for a few species of archaea that utilise a specially adapted lipid monolayer. It has even been proposed that the very first form of life may have been a simple lipid vesicle.
Protocells: A self-organised, ordered collection of lipids proposed as a rudimentary precursor to cells during the origin of life. A central question in evolution is how simple protocells first arose and how their progeny could diversify, thus enabling the accumulation of novel biological emergences over time (i.e., biological evolution). Although a functional protocell has not yet been achieved in a laboratory setting, the goal of understanding the process appears well within reach.
Earth was formed about 4,500 million years ago (Mya). Life began to appear in the sea about 4,000 Mya. The first living organisms were prokaryotes (single cell creatures with a surface membrane, but no nucleus – pronounced as proh-CARE-ee-ohts), and single cell eukaryotes (with a cell nucleus), from about 2,200 Mya. Multicellular eukaryotes appeared in the sea about 1,600 Mya. The earliest land plants date from about 580 Mya, and land animals from 500 Mya.
The present position in the taxonomic classification of life on Earth puts all living matter into three “kingdoms”: plants, animals and fungi. This classification does not include organisms too small to see with the naked eye, such as microbes, bacteria, viruses, etc.
Animals are distinct from plants and fungi in many ways, but one way is that animals alone have a nervous system comprising neurons. It is neurons that give animals the ability to have coordinated movement, to think, and to have consciousness and intelligence. It is neurons that collect information from the senses such as touch, vision, hearing, taste, and smell, and which transmit this information to the neurons that process information within the brain, and to the neurons that control muscles and movement. The white thread-like data channels throughout the body that we call “nerves” are actually the axions of neurons.
The animal that has found its way to the “top” of the evolutionary tree, the apex predator here on Earth is Homo sapiens, a species of human. It is a puny animal that has no bodily weapons such as sharp teeth and claws, and can’t even run very fast. It has achieved its top position by having great intelligence, an amazingly effective verbal language, and dextrous hands. These qualities are entirely due to the neurons of its nervous system. But has the evolutionary progress of human beings peaked, and are the physical and mental qualities of the human species now in decline? Is this decline hidden by the continued growth of knowledge? We no longer breed from our “best” and strongest. The fastest rate of breeding now tends to occur within religious groups and poverty-stricken communities.
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The creation of machine life
A recent development in Artificial Intelligence (AI) is the application of artificial neurons. These work on the same principle as biological neurons. Impressive recent steps in AI, such as Deep Learning, image recognition, Natural Language Processing, and products such as ChatGPT, rely on such neurons.
Seeing as biological creatures and AI programs share comparable neuronal technology, is it not logical that anything biological organisms can do, can also be done in principle by machines? We're not there yet, but AI with neuronal content only began a few decades ago. It's early days. Animals have been evolving their neuronal systems for 500,000,000 years. The human being, with its intelligent neuronal system, has been in existence for about 500,000 years. Although the evolution of human beings may have peaked and may now be in decline, the evolution of thinking machines has hardly started. They can carry on when we go extinct.
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