Able to look back on the evolutionary process, the process seems to have been relatively simple. The first animals to walk on land were fish. Then reptiles acquired feathers and developed flight. Eventually, primates evolved into humans, who are capable of doing tasks like juggling, writing symphonies, and creating spacecraft.
But it was a long, winding road that took us from primordial soup to where we are now. This has long been seen by paleontologists in the fossil record. Today, we can use DNA to illustrate the numerous detours, mishaps, and conflicts that make up the story of life, owing to scientific advancements.
Understanding the evolution of life on Earth is now more accessible than ever. But as you’ll see in these blinks, the reality is much more complicated.
These chapters will teach you;
- how fish were able to breathe air before they had the ability to walk on land;
- that you have more similarities with a sea squirt than you likely like to acknowledge; and,
- why does the lightning-fast tongue of the salamander have to develop in the manner that it did?
Chapter 1 – Rather than acquiring new qualities, plants and animals adapt by repurposing existing ones.
Paleontologists have been preoccupied with the subject of how a fish may have developed legs and started walking on land for decades.
The author is a paleontologist who wondered the same things that Charles Darwin’s contemporaries did about his idea that evolution is a process of intermediate phases. Why, for instance, did the ancestor of a bird without wings develop the appendages that would later develop into wings?
Why wouldn’t useless wings vanish instead of growing? The response is not that little wings developed into large wings. The fact that what we currently refer to as wings was originally something else. Nothing begins where you believe it does is the author’s new maxim, which was motivated by Darwin’s retort to his detractors.
The way we understand the evolution of life has been permanently changed by Darwin’s claim that new traits appear as a result of old ones altering their roles. Take a peek at the meek fish to see how to do it.
A particular fish that a French scientist had discovered in Egypt in 1798 rose to fame. Why this specific fish? Well, its body had peculiar air sacs. Now, the majority of fish have air sacs called swim bladders, which keep them submerged at a particular level of water. The air sacs of the famed fish, however, were unique. The fish’s esophagus was where they were attached. They were a pre-lung.
Scientists started searching rivers and lakes worldwide in a frenzy to get additional information. Surprise! This Egyptian fish wasn’t all that extraordinary after all. Numerous fish had the same proto-lungs. Fish that breathed air weren’t the exception; rather, they were more or less the norm.
According to recent findings, swim bladders and proto-lungs are two separate species of the same organ. In addition, the genes that create swim bladders and lungs are the same in fish and, as we’ll discover in a moment, in humans as well.
Fish have had lungs for a long time to help them adapt to life on dry ground. Instead, fish were already inhaling air before they emerged from the water. The air sacs of fish have simply been repurposed by evolution.
See? Nothing starts where you expect it to be.
Chapter 2 – For both people and species, embryos contain the key to how change occurs.
Embryos and the process of developing from egg to adult are thought to hold the key to understanding how species differ from one another. The first significant development, however, occurred in 1865, when French scientist Auguste Duméril glanced into his aquarium and saw a startling sight.
A Mexican salamander species had been imported by Duméril months before. He was suddenly faced with two separate species of salamanders, as though the parents had produced hybrid offspring.
The examination that followed this incident, which appeared odd, had significant effects on how scientists examine evolution.
Duméril got fixated on the enigma surrounding the two salamanders. He got to work after asking his housekeeping employees whether they had tampered with the aquarium in a strange manner. He concluded that there were two potential developmental paths for the embryos of this particular species of salamander. It depends on the situation they were in as to whatever route they picked.
Salamanders from Mexico’s indigenous population were aquatic creatures. They thus possessed fully formed traits, such as a fin-like tail and webbed feet, to aid in swimming. However, because their progeny had grown up in a dry environment, their growth was halted, and they developed tails and limbs that were more appropriate for dry ground.
The extent of Duméril’s realization could appear to be limited. But in the end, it has allowed researchers to identify the origin of all vertebrates, including mammals, birds, amphibians, reptiles, and fish.
It might not be an ancestor that you are particularly pleased to claim as your own. The sea squirt, a lumpen organism that spends virtually its entire existence attached to a rock, is the mother of almost all animal life on Earth.
But the sea squirt makes up for its lack of glamour with genetic grace. The sea squirt travels freely across the water as a tadpole-like embryo. It loses almost all of its connective tissue within a few weeks, along with its tail, nerve cord, and gills. It attaches itself to rock after floating to the ocean’s bottom.
The origin of all vertebrates may be traced back to a sea squirt that prematurely ceased developing millions of years ago – similar to the salamander. For whatever reason, the person retained their nerve cord and connective tissue and matured into adulthood with all of their juvenile traits.
Later, we would adopt their characteristics as our own.
Chapter 3 – Even little errors in DNA can have significant repercussions.
You might wish to skip this section if discovering the truth about your sea-squirt origins upsets you.
You are undoubtedly aware that parents pass on their DNA to their children. You might be surprised to learn that during the four billion years of life’s evolution, it has also transferred from ancestors to descendants. That implies that a sea squirt and you have some DNA in common.
You are obviously smarter, more educated, and physically closer to perfection than a sea squirt; how then can it be that you share DNA with a bizarre blob on the seafloor? The distinctions between our genomes hold the key to the solution. Even more than by analyzing fossils, scientists may learn about the links between species by examining the ways in which genomes vary.
The hundreds of amino acids that make up proteins, which are themselves built up of proteins in a certain sequence, are what makeup DNA. A genome is the DNA of a plant or animal that is properly organized.
Genomes care about the order. How do genomes, however, arrange themselves? A switch is a solution. Switches are just instructions for when and where to add each piece of the genome, to put it simply. This process begins when an embryo develops inside its mother and lasts all the way until maturity.
Switches are crucial because even the smallest deviation from the expected sequence might cause the entire system to malfunction. One amino acid, for instance, can make all the difference between healthy red blood proteins and sickle cell proteins, with potentially catastrophic results. According to the author, about 70% of sickle-cell anemia patients pass away before the age of three.
But occasionally, a broken switch might trigger a shift that propels evolution. Recent studies have revealed that every significant change in the development of animal bodies, from skulls to limbs and fins to wings, is the result of alterations in switches. There are no modifications to the genes themselves as a result of these evolutionary alterations. They are modifications to the switches on/off timing and location.
What does this mean for the distinction between you and a sea squirt, then? You don’t have a huge intellect and the capacity for offense because of a difference in your genetic makeup. It resides in the switches that regulate how your genes function.
Chapter 4 – Gene alteration or mutation has led to very rapid evolution.
Darwin believed that natural selection served as the engine of evolution and that individual variation served as the fuel. Individual variation might, of course, also indicate mutation.
When you hear the word “mutant,” you might picture futuristic Frankenstein creatures. Darwin, though, found it to be somewhat less spectacular. A mutant is simply a person who exhibits a characteristic that differs from the norm in terms of appearance or behavior. If having that characteristic makes a person successful, they will pass it on to the following generation. It is likely that the character will eventually disappear if it reduces their chances of success.
There are two distinct mutational modes. First, there are differences in organ size or degree. The existence or lack of structures, such as additional fingers or kidneys, is the next type of variation.
We can learn more about how genetic information is transmitted and how evolution works by examining mutants. Scientists discovered, for example, that the location of genes on DNA chromosomes mirrors the shape of the body after researching fruit fly mutations. The genes involved in developing the head are located at the top of the chromosome, those involved in developing the belly are located in the center, and so on.
This alone was a significant finding. But what occurred next sent shockwaves across the scientific community.
It turns out that this was true for a large number of species, not only fruit flies. We share the same top-down, muscle-building gene sequence on our chromosomes with flies, frogs, worms, and even people. After making this finding, researchers could finally answer the riddle of how animals evolved.
Soon after, they discovered something more. From frog legs to blue whale flippers, the same genes cause the creation of limbs in a wide range of species. Fish have them too, but instead of limbs, they produce fins. Furthermore, these genes in fish are active and drive the growth of the bones that sit at the tips of the fins.
Chapter 5 – The human genome contains fundamental components that enable copying, mutation, leaping, and even hunting.
You could be excused for assuming that with all that humans have accomplished, our bodies are significantly more developed than those of our closest ancestors, and certainly more sophisticated than fish or plants. But if the sea squirt has anything to teach us, it’s that our conceit that we are the world’s top predator is unjustified.
Our genome is the clearest example of this anywhere. It seems logical to think that our genome functions like a well-tuned machine with everything in perfect alignment and playing together as gracefully as a professional symphony. But such a supposition is incorrect.
The human genome is extremely dynamic, and its constituent parts are always at war with one another.
Actually, the amount of genetic material in an animal has nothing to do with how complicated it is. Corn, which contains twice as much genetic material as you do, is an excellent illustration of this.
In actuality, a large portion of animal DNA is made up of duplicated, essentially useless genes, or “junk DNA,” as it is known to scientists.
However, the active genes in the genome are hard at work and act in a variety of unanticipated ways. Chromosomes divide and duplicate themselves during the production of sperm and eggs. This is advantageous because the new gene acquires a new function while the old gene keeps its original one. However, this process went awry somewhere in the distant past when genes learned to leap.
That’s correct; genes not only have the capacity to duplicate themselves, but also the mobility to bounce across the genome and do so. Barbara McClintock, a Nobel Prize-winning American scientist, estimates that these jumping genes make up around 70% of the human genome.
However, if you were beginning to feel bad for the typical DNA segments that these leaping upstarts were taking over, rest assured they are quite than capable of defending themselves. Jumping genes have a manner of being physically weighed down by normal DNA segments, which prevents them from hopping to another spot.
Jumping genes are controlled by this method, although they can still replicate in certain ways.
Chapter 6 – Even if evolution had taken a different course, many results would have remained the same.
As we now know, the sea squirt is the progenitor of all living things on Earth. But a different revolutionary event created the groundwork for life as we know it billions of years before the sea squirt.
Single-celled organisms were the first biological things to exist on Earth. The Earth’s atmosphere gradually began to fill with oxygen as a result of some of these creatures beginning to manufacture oxygen as a waste product over time. After countless billions of years, a new type of microorganism that derived its energy from oxygen started to proliferate. The development of bodies was made feasible when these germs joined forces with a bacterium that could generate complex proteins.
Scientists were in awe of this history and what followed for a very long time. They reasoned that even the smallest deviation would have upset the balance. They were mistaken.
Let’s go back to our old buddy the salamander to demonstrate the shocking reality that some events would have occurred anyway. Perhaps you’ve seen movies of a salamander using its mouth to grab a fly. Even in slow motion, it is difficult to see the tongue coming out of its mouth so quickly. Then, almost instantly, it pulls it back into its mouth. It is a true biological marvel and a remarkable example of evolution.
The truth is that there aren’t many species of salamanders with projectile tongues that are linked to one another. Their ancestry is essentially wholly different. This indicates that the evolution of a projectile tongue had been placed more than once—possibly even more than three times. Additionally, each development happened separately from the others.
There can never be more than a finite number of solutions to a problem, which is why multiples like this are necessary. Consider flying. In order to produce lift, a creature needs a large surface area, which is why all flying creatures have wings rather than, for example, helicopter blades.
It should not be surprising that humans occasionally have multiples of the same item as all creatures employ different copies of the same genes to develop their bodies. Great technologies like flying and projectile tongues did not just appear by chance.
The dice are definitely thrown, but life’s history is not a game of chance. The way our genes construct our bodies, the physical limitations of our surroundings, and history all have an impact on how we have developed.
Some Assembly Required: Decoding Four Billion Years of Life, from Ancient Fossils to DNA by Neil Shubin Book Review
The tale of life is a winding one, with conflicts over genetic dominance, dead ends, and incorrect turns. But there are astonishing and unexpected genetic commonalities across all creatures. Even if we observe some unexpected evolutionary results, this connection suggests that some of those outcomes may not be as absurd as they first appear.