The "Real" Missing Link in Human Evolution

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The "Real" Missing Link in Human Evolution

The ability of the sequence to combine different portions of the DNA is completely different from how a new gene is typically created / Photo by Getty Images

 

Many of us have heard the term “missing link,” which spurs the imagination about a species that came before homo sapiens roamed the world. However, from genetic investigations to uncovering new human fossils, it turns out that the way that most people view this concept is greatly misguided.

 

A Huge Misnomer

While many picture evolution to be a chain where one species alive today is directly descended from an ancient species millions of years ago, this is not the case at all. Many paleontologists actually disagree with the term “missing link,” as it connotes a linear chain of evolution when it is more of a tree where several species have the same ancestor, and some can even live alongside their supposed ancestor species. The reverse is also true: not every species seen today can be traced back to a single evolutionary parent.

 

The Tree of Evolution

For many, the phrase “missing link” is meant to apply specifically to humans and how our species came to be set apart from the ape family. We often picture a creature that is somewhere between half-man and half-ape, which we could easily slide into a picture show between chimpanzees and the modern man. However, there isn’t one particular human ancestral fossil that can give us a specific picture of the transitional phase from ape to man. Instead, we have several specimens of human fossils that can show us that evolution was a straight path but a winding journey.

The story of how humans became what they are today is one that stretches several hundreds of millennia. The way that we walk, with backs upright and legs beneath us, was an evolutionary change that happened fairly early. Scientists have even found, according to Smithsonian.com., that our prehistoric ancestors were already walking this way anywhere from 6 to 3.6 million years ago. This was found through preserved remains of footprints walking through ash.

 

Our Genetic Code

The term missing link, while a misleading one, may have a different connotation than what most people expect. Some scientists believe that the missing link is not a specific species in itself, but a link in our genetic code.

Sometime about 8 to 12 million years ago, the ancestors of the great ape species, of which we are close cousins, had a dramatic change in their genetic makeup. Some of the pieces of their DNA were copied and spread across many chromosomes. Along with these, however, came a few additional segments of DNA. The resulting pattern continued to spread down onto the next branches of the evolutionary tree, and the genome remains particular to the great ape family, including gorillas, chimpanzees, and also human beings.

Many scientists have attempted to find out the function of this string of genes. Many have gone so far to say that they’re the missing piece of human evolution or that they are the code that was meant to bring about a new string of genes. However, the experts at least know that they are linked to new cell generation, as well as brain development and increase of brain size.

 

A Missing Explanation

The gene regions, though potentially ground-breaking in the study of the origin of the human species, have unfortunately gone mostly unexamined and unexplored. This is because the sequence that makes them up has a repetitive structure with several duplicated parts.

Though this may sound like it would be easier to analyze, the way that geneticists study DNA sequences is by pulling them apart and then putting them together to make sense of how each section works. Disassembling and reassembling a sequence of parts that are essentially repetitions of each other would be like putting together a puzzle with the pieces looking more or less the same. Many conventional genome scientists have outright given up on sequencing the entire thing due to their complexity.

Some scientists believe that the missing link is not a specific species in itself but a link in our genetic code / Photo by Biswarup Ganguly via Wikimedia Commons

 

Changes in DNA

These stretches of duplicated sequences that occur repeatedly in a specific chromosome have since been dubbed as “core duplicons.” It seems that these cores, by some mysterious function, are able to duplicate other neighboring sequences of the DNA around it. While serving as the anchor or the focal point, they then reinsert the new copy of the duplicated sequence into a new location. They can even bring together two unrelated pieces of DNA, which leads to the DNA having new functions.

While the core duplicons are highly unstable, they also seem to be a precursor to evolutionary changes. The ability of the sequence to combine different portions of the DNA is completely different from how a new gene is typically created. Usually, an existing gene would simply be copied and would develop new function on its own. In fact, according to Scientific American, core duplicons have played a large part in the genes that have greatly increased the size of hominid brains.

Researchers are still working hard to uncover the remaining pieces of knowledge that will lead us to a better understanding of our ancestors, and ultimately, ourselves.

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