Misconceptions about evolution exist due to humans’ inability to comprehend the enormousness of time. That leads to common misconceptions such as, “I haven’t seen a monkey giving birth to a human”, “if humans evolved from monkeys, why do monkeys still exist?” etc.
Firstly, monkeys did not evolve into humans. In the evolution tree (remember: it’s a tree and not a line), monkeys are not our ancestors; they are cousins. In other words, the common ancestors of monkeys and humans (apes) existed about 30 million years ago. The monkeys we see today had a trajectory from that time to the present, just like their distant cousin, humans, in that period.
The same goes for chimpanzees and humans. Chimpanzees are our closest cousins, and that branch goes back 5-7 million years ago. A rough sketch of the branching business is shown below.
Understanding Evolutionary Trees: Evo Edu Outreach (2008) 1:121–137
Take a carrot, cut a slice, and look closely. Does it resemble your eyes? See what I meant; it provides the nutrient that is good for the eyes. Have you ever wondered why the tomatoes cut through the middle appear like your heart? Do you know that the polyunsaturated fats of walnut boost your brain? Don’t you know kidney beans are the best thing for your kidney?
The seed for the brain
Start with Mr Walnut. Here is what it looks like:
So naturally, it should be related to the brain. Isn’t it? Well, let me search: yes, it has polyunsaturated fats that are good for the brain! Well, that can also be good for the heart. But that is not the point. And it does not resemble my heart. What about sunflower seeds, flax seeds or flax oil, and fish, such as salmon, mackerel, herring, albacore tuna, trout, corn oil, soybean oil, and safflower oil. They all can give you similar nutrients. But they don’t look like a brain. So, let walnut be the brand ambassador of my brain. Why not? By the way, Cahoon et al. searched the literature but could not find any strong association between walnut and cognitive power. Maybe, they did not search deep enough!
Carrot for your eyes
Cut a carrot and see if it appears like your eyes.
No? If not, cut it until you see some part that resembles your eyes. Come on; you can do it. But what about these: tomatoes, red bell pepper, cantaloupe, mango, beef liver, and fish oils. They, too, contain vitamin A. So what?
Vitamin A is not going to give you night vision. But it should be part of your diet as it helps manage your health, including eye health. Also, carrot doesn’t come packed with vitamin A. But it contains its precursor beta carotene.
Kidney beans
What is the difference between kidney beans and other lentils? Or between blueberries, seabass, egg white, garlic, olive oil, bell peppers, and onions? Well, the key difference is that except for kidney beans, none of the others resembles my kidneys. So, even if they are better food for kidneys than these beans, I am not interested in them.
What about eating jelly beans? Something to research on.
Where do these come from?
Human beings are masters of finding patterns around them and making up stories to support their imagination. The doctrine of signature, too, belongs to that category. It is also a favourite for the creationist folks. Why else is that food created with the shape of your organ? There must be a purpose.
Walnut intake, cognitive outcomes and risk factors: a systematic review and meta-analysis: Pubmed
Cooking Legumes: A Way for Their Inclusion in the Renal Patient Diet: Pubmed
You may know that our cell nuclei contain genomic DNA – parts of it possess the codes (genes) that determine all the traits. We obtain this from our parents through some combination.
Enter mitochondrial DNA (mtDNA). It is not your usual type. First, it lies inside mitochondria and not the cell nucleus. Second, it is inherited from the mother alone; fathers do not contribute. Third, it does not recombine. What is so special about this? Well, mtDNA has become the tracer molecule to study relationships between one individual to another.
The absence of recombination and bi-parenting inheritance made these molecules scientists’ pet for tracing the maternal ancestry of human beings. And they traced back thousands and thousands of years and ended up at a single mother who lived ca. 200,000 in Africa. She is called the Mitochondrial Eve. She was not the first human but became the meeting point (common ancestor) when human mtDNAs were all traced back.
If our great grandmother Lucy was the bridge between non-hominins and hominins, Tiktaalik was that extraordinary life that acted as the connection between fishes and four-legged animals. I know it’s not easy to digest that we had fish as our common ancestor!
On the one hand, it was a fish with scales and fins. Unlike the other fishes, Tiktaalik’s fins had bones (corresponds to an upper arm, forearm and wrist) that could enable them to come out from the water and walk. And it had lungs and grills. Above all, Tiktaalik was a fish with a neck.
In his book, the Inner Fish, Neil Shubin, the American palaeontologist and evolutionary biologist, narrates the journey to unearth nature’s best-kept secret for a long time (about 375 million years!) – discovering the missing transitional piece from the life in water to life on land. The possibility of transitional creatures was something Charles Darwin had predicted some 130 years before!
Lucy: wiki Tiktaalik: wiki How fins became limbs: nature A Devonian tetrapod-like fish and the evolution of the tetrapod body plan: nature
This post is not a commentary on the book Selfish Gene by Richard Dawkins, although I do recommend the book. But this is around how to understand what is selfishness.
It seems scientists often forget about the common public when it comes to naming their books or concepts. That way, the title, selfish gene, is just another one: survival of the fittest, natural selection, god particle, the list goes on. None of these phrases represents what they truly meant. God particles have nothing to do with god, survival does not correlate with any physical fitness, or there is nobody in nature to select or reject anything.
Selfishness in biology simply means the ability to survive no matter what. It has little to do with a species’ deliberated actions using its brain, such as mating (or not mating), not sharing resources, stealing or killing. It only means making copies and preserving genes by passing from generation to generation.
What a headless virus can do
Take the case of the most popular show in town, the novel coronavirus, SARS-CoV-2 or Covid-19. The virus has two parts, the outer envelope, which has a bunch of proteins, including the famous spikes, all embedded in a lipid membrane and the inside material that contains the genome, a single-stranded RNA, preserved nicely on a protein called the nucleocapsid or N-protein. The genome is long and contains information to make new viruses using someone else’s workshop, the human cells.
The virus thus mobilises human cell machinery (e.g. ribosomes) to replicate. It creates billions of copies that infect millions of people. And the virus does all these without having a body or a brain!
Brain doesn’t need to follow
Human genes, too, want to preserve themselves. They are also selfish and want to be immortal. But it has a master, the human brain, which can overrule the instincts for the greater good. It may have inherent altruism, but more importantly, it is trainable based on a value system. While the brainless gene wants and will long for eternal life, you, as a human, can prefer not to have offspring. You may stop taking sugar, run for hours when no lion is chasing, donate organs to strangers.
Sexual selection is a topic that invoked some controversy among evolutionary biologists. Darwin distinguished sexual selection as the difference in the ability to produce offspring, and natural selection, on the other hand, is about the struggles for existence.
Sexual selection is a combination of many factors. It could be a male-male struggle to reach a female, females snubbing males with certain features, or simply mating with certain males leading to weaker or no offspring.
mtDNA and NRY know it all
Whatever may be the precise reason, it has been established now using complex DNA analysis and computation that historically, more females and fewer males have participated in the development of the human race. In other words, throughout human history, leave the modern time when females started moving with their partners, fewer men participated in the reproduction process, although there are no reasons to believe that their respective numbers in the population were different. It went to such a low around 8000 years ago when the female-to-male effective population ratio was about 17!
References
Lippold et al. Investigative Genetics 2014, 5:13, Human paternal and maternal demographic histories: insights from high-resolution Y chromosome and mtDNA sequences
Genome Res. 2015 Apr; 25(4): 459–466, A recent bottleneck of Y chromosome diversity coincides with a global change in culture
Industrial melanism is a term to familiarise. Biston betularia, the “poster moth” of evolution through natural selection, made this word immortal. You may call it a victim of the Industrial Revolution (or the coal pollution of England). However, the transformation of this humble creature provided the most powerful illustration of the theory of evolution and accelerated its inevitable journey towards becoming a theorem.
To give a brief background: Biston betularia is a type of peppered moth that had transformed from its pale (typica) form to black (carbonaria) in the last decades of the nineteenth century, coinciding with the industrial revolution in England. The hypothesis for the observed shift is that the pale varieties became prey to the bird predators as the former had become easily distinguishable on the blackened walls of industrialised cities of England, thanks to the coal revolution (and pollution). Accidental mutant varieties with black shades saved themselves from the lookout of the predators and became the most abundant species in the 20th century and continued until a few decades ago.
We have seen it before but repeating. Polymorphism is where two individuals differ in their DNA sequence, and the less common variant is present in at least one per cent of the people tested. The simplest type of polymorphism is when there is a single-letter change in a genetic sequence. That is called a Single Nucleotide Polymorphism (SNP).
Scientists have recently discovered the locations (the sequence and the genes) of the mutations that caused the change of colour from pale to dark. Further, analysis by statistical inference has found that the transposition happened around 1819, consistent with the actual observation of the change (from the dominance of the pale population to the black).
Noone sees its evolution!
The story of the peppered moth’s evolution is both fascinating and confusing. First, we need to realise that an individual white moth never transforms into a back one in its lifetime; the celebrated illustration (The Road to Homo Sapiens) of Rudolph Zallinger may tell you otherwise. It was a crime, though unknowingly, the artist committed against science that etched this faulty image – of an ape transforming into an upright man – permanently into the human psyche. Evolution is not a conscious conversion of one species to another. For example, the original white-moth-dominated society and the new black-dominated can easily have a hundred generations of separation.
Humans, the moths of glass sponges
We can see a moth’s evolution in front of us because a moth has a short lifetime – a few months at the maximum. In other words, given a few decades, we could see a few hundred life cycles of moths. Human evolution is not visible to humans because we can never see a thousand generations of ourselves unfolding before us. That is why we go after evidence, and science delivers. In doubt, ask a glass sponge who has survived this planet for 10,000 years!
The industrial melanism mutation in British peppered moths: Nature
What is the probability of creating a fully developed animal or a human being? Creationists often use this argument to challenge science, but that is understandable. What is depressing is to see many scientists, too, falling into their trap.
Look at this mind-boggling probability. Think about one biological molecule in our body – haemoglobin. The molecule consists of 4 chains of amino acids, and each chain is about 146 links consisting of a possible 20 amino acids. So, to get a functional molecule, it needs to get one right out of (20)146 options. How is it then possible to have the whole human body created? Since your random processes can’t explain such ‘beautiful crafts’ of nature, you better accept my design theory!
It is a valid question, except that today’s complex systems are not formed like this. The answer lies in evolution. You and I are today because of the accumulated small changes. Not from any single change. Getting a small change is relatively easy, with about a few million unforced errors happening every day.
The complex systems we see today all originated from simpler systems. And those simpler ones, from even simpler ancestors. Until the stage, when the first life, some RNA-based self-replicating molecule, was formed! And how are they made? By chance in the chemistry laboratory of the earth using simple gases in the presence of heating, cooling and lightning. Stanley Lloyd Miller and Harold Clayton Urey proved that in 1953 by using methane, ammonia, water, hydrogen, and electric discharge to produce amino acids. Subsequent works of scientists synthesised the building bases of RNA from simple molecules.
In my post on SLC24A5 or the one on plant breeding, we have seen that a simple change in a random gene location can produce wonders. Think about it. There have been 3.5 billion years passed since the first life. Millions of trivial changes happened, a few of them passed through the sieves of nature, and a number of them got rejected to extinction. It is called natural selection.
Most of the food you eat today is genetically modified, if not all! By genetic modification, I do not mean that the cultivar had gone through countless Petri dishes and a bunch of scientists injected solutions that would consciously and systematically modify specific parts of its DNA. Much milder than that, through a process called plant breeding, a fundamental process in agriculture.
Let me go a step further: humans cannot (or would not) make the transition from the Hunter-Gatherer society to the Agrarian without violating the rules of natural selection. We have seen Natural Selection before, and I want to repeat: Nature does not select anything. Nature only offers its playground and let the living species play random games. Some survive the game; we only get to see the survivors.
Humble Story of Staple Grains
Take wheat, rice and corn, which satisfy more than 50% of the calory requirements of the world. They all had their beginnings as grasses that bore too small seeds to attract any animals. Wild wheat seeds grew at the top of a stalk that spontaneously shattered and spread as far as possible, away from public sight, and quietly germinated. For that reason, they escaped early humans until a single-gene mutation caused a few plants to lose the capacity to shatter. For the wheat plant, this would be detrimental for the seeds cant fly to places and germinate. By the way, if I made you think that the plant was doing all these out of intelligence, let me rephrase – plants with such a defect won’t survive for long because of their limited capacity to spread their offspring.
However, such useless mutants were a lottery for humans as they got control of the entire growth and regrowth of the plants without losing any seeds. Wheat is now in her orchard. Occasionally, the already ‘unnatural’ plant gets another mutation, yielding larger seeds. From the plant’s viewpoint, what happened is a sheer wastage of its nutrients; after all, a seed, irrespective of its size, gets a single chance to become the next plant. Humans, on the other hand, love it and select only those bigger ones and grow.
For centuries we did this process without knowing what we were doing. Now we know the details, so much so that we know what parts of its genetic make-up need to change. And we also know how to change it!
This one is going to disappoint some of you. What causes cancer? The answer is – life. Cancer happens; well, most of the time!
Primary reasons for cancer in humans are classified into three categories: environmental (E), hereditary (H), and mistakes during DNA replications (R).
Researchers at Johns Hopkins University evaluated cancer incidence in 69 countries and found correlations between cancer risks and these factors. Before going into details, please see the picture that I copied from Tomasetti’s paper (Tomasetti et al., Science. 2017 March 24; 355(6331): 1330–1334. doi:10.1126/science.aaf9011.).
First, a primer on what I meant by the replication factor, R. Approximately three mutations occur every time a stem cell divides. Most of these are inconsequential to us, but occasionally, they cause trouble. What is so special about stem cells? Stem cells are the body’s prime cells that give birth to cells with specialized functions – the blood cells, brain cells, heart muscle cells or bone cells.
Leading environmental factors known to cause cancer in humans include UV from sunlight, tobacco, soot, asbestos, carcinogenic chemicals, and ionising radiation.
Randomness, Again
These results also partly explain the observed stochastic nature of the disease. Remember, “my granny had cancer without smoking, and my uncle still smoking healthy”, all that stuff! Now you know the reasons for the deadly outcome are many – some you know already, some don’t, and perhaps never will.
Not an Either Or
Results from the study also point to the human tendency to rush to wrong conclusions, similar to a deductive fallacy. Environmental reasons are responsible for some cancer types, but it does not mean all cancers are due to Environment. To be precise, two in three are not! Does it mean you ignore environmental factors, smoke, eat tobacco, and give up sunscreen? Quite the opposite. One must continue avoiding exposure to carcinogens as they are the levers to manage those individual probabilities that are within your control, which eventually leads to a reduction in the combined chances of getting the disease (remember the AND rule of probability?). You thus avoided the disease, at least for a while!
The last takeaway of the study, which showed Pearson’s linear correlation of 0.804 between total stem cell divisions and lifetime cancer risk, leads to an unwanted prize for achieving higher life expectancies – the more you live, the more your chance of dying of cancer!
