1. Evolution doesn’t always lead to greater complexity
Evolution has produced umpteen trillions of combinations during the short history of life on earth, the vast majority of which has been lost forever. From what we have left, it seems as though there are some organisms that are more complex than others. Humans, with our 39 trillion cells, seem more complex than an amoeba, say, which survives as a single cell.
Not so fast though. There is an amoeba with a genome measuring over 600 billion base pairs in length, which is about 300x larger than the human genome.
Natural selection can lead to greater simplicity. Exciting explorations into caves absent of light reveal insects and other life forms that look very similar to those above ground, except they have lost their eyes, for example. What needs eyes in perpetual dark?
Many species across the tree of life have, indeed, become more simple rather than complex. There are several researchers these days interested in whether our ancient animal ancestors, which gave rise to humans, snails, sea sponges and anemones, for example, were more complex than we had previously assumed. Perhaps some of the very simple seeming sponges and placozoans are a lot more simple than the most recent common ancestor which we all share.
2. The tree of life is more like a complicated web
You have to prioritise – Rather than a tree, it’s good to imagine a web of life. This is especially important, as the more we learn about the mechanisms of evolution, the more we realise that the idea of there being distinct species is often a loose concept.
In bacteria, for example, ᴠɪʀᴜses have a huge role to play in driving evolution, while bacteria also like to exchange genetic material willy nilly, through a process known as horizontal gene transfer, which is one of the drivers of the spread of ᴀɴᴛɪbiotic resistance. Even among Homo sapiens there are about 42 or so ᴠɪʀᴜs genes that have become part of our genetic makeup after ɪɴꜰᴇᴄᴛing us, then staying with us down our distinct evolutionary path.
Let’s face it, most of us have a little Neanderthal or Denisovan in us, long after these species diverged from our common ancestors. Put simply, evolution is not linear, but involves lots of criss-crossing lines.
3. Evolution is actually a really old idea
Empedocles [Greek philosopher, Sicily, 495-435 BC] believed that the universe consisted of four elements: air, water, earth, and fire. The forces of attraction and repulsion acted on the elements, causing them to create the universe and everything within.
He believed these forces formed humans and other living creatures from mismatches of different body organs. He then suggested that as desirable combinations persisted, the others ᴅɪᴇd off.
Lucretius [Roman philosopher, born 94 BC in Pompeii] created a follow up theory. He suggested that that humans with the best features for strength, speed, or intelligence survived while the rest ᴅɪᴇd off. He also added that the elements and forces that Empedocles wrote about only created humans by chance.
Anaximander [Greek philosopher, Miletus, 610 – 546 BC] wrote that a species could evolve to create another species – he suggested that a fish birthed the first human.
4. No one organism is more evolved than another
As much as we like to think that everything revolves around us, it doesn’t (although a substᴀɴᴛɪal number of people still think that the Sun orbits the Earth, it doesn’t!).
We tend to look at the universe from an anthropocentric perspective (Gods notwithstanding), which makes sense, but tends to see us putting people ‘on top’ of the tree of life. There might even be a belief that humans are somehow ‘more’ evolved than chimps, or any other life form, but this is simply not the case.
Humans have had exactly the same amount of time to evolve since the beginning of life on earth as any other organism on earth. We’re the tip of a very long branch that has somehow survived the perils and passages of time over the last 3.5 billion years or so. We’re as ‘evolved’ as Salmonella, a carrot, or Paul the psychic octopus.
The “tree of life” can make it look a bit like a procession, from bacteria at the ‘bottom’ to humans at the ‘top’.
It is far from clear cut, however. For a start, there is biology’s dark matter, which is comprised of millions upon millions of different species, many of which we have yet to discover, of protists. These organisms can be more plant like, or more animal like. Some of them act a bit like animals and plants at the same time, roving around using an eyespot to guide them, eating other small organisms, while simultaneously using sunlight to make sugars through photosynthesis.
Some of those organisms share very similar characteristics with you or me. The rhodopsins in our eyes, for example, which help us to form an image of the world, have ancient ancestors in the eyespots of green algae, which come far closer to plants in the grand scheme of things. Of course, plants don’t have eyes.
5. What does it mean to be human? We’re not alone.
There are more bacterial cells living in and on you than there are human cells that make up your body. There are fungi and archaea, too, and together these non-human cells make up the microbiota which helps us to digest food or defend against ᴅɪsᴇᴀsᴇ. Our microbiota is pretty much established by the age of three years old. It’s passed on in the birth canal and picked up from the environment, such as the food (or soil) that we eat as toddlers.
You might think, yes but these microbes aren’t what make me, me, but there is increasing evidence that we rely on our gut microflora for much more than digestion or protection. What about the gut-brain axis? They say you are what you eat, and it’s not as far-fetched as you might have thought. The microbes in your stomach go some way to informing your thoughts and feelings.
So who is pulling the strings? Are we just vessels for the microbes that live in our guts? We are certainly beginning to understand in much greater depth the effect that microbial communities have on our own boᴅɪᴇs, and perhaps our mind.
If this sounds far-fetched, there is evidence to suggest that the toxoplasma parasite (which we catch from cats, and possibly pink lamb) might cause us to be more extroverted, which makes evolutionary sense, as the parasite is known to ‘manipulate’ rodents (a secondary host) through remodelling their DNA slightly, making them less likely to avoid the cats which the parasite relies on to reproduce (the primary host) – thus increasing the likelihood that the parasite does indeed reproduce.
Brain-controlling parasites are pretty common. There are fungi that turn insects into zombies, which climb to the highest possible point before sᴜᴄᴄᴜᴍʙɪɴɢ, allowing the fungus spores that erupt from fruiting boᴅɪᴇs of the insect ᴄᴏʀᴘsᴇ to spread far and wide on the wind – even persuading other insects to come and inspect the ᴄᴏʀᴘsᴇ and pick up the ɪɴꜰᴇᴄᴛion themselves.
Then there are the wasps, which inject ᴠᴇɴᴏᴍ and eggs into the prey of their larvae, which only hatch once the unfortunate victim has been ʙʀᴀɪɴᴡᴀsʜed into collecting food and making a nice little parasite nest for its incumbent.
It makes you question your ideas on free will, whatever that might be.