How Are Humans Fundamentally Different From Animals
"What makes the human superior to field animals?" So mused King Solomon, the wisest man of his times (10th century BCE), in Proverbs. Since then the question of how humans are different from animals has occupied the best minds of the human race. That ranges from Plato in the 5thursday century BCE to the molecular biologists, neurobiologists, neuropsychologists, and philosophers of the 21st century.
For a long while, we thought that information technology was intelligence that set up usa apart. But, we now know ameliorate. Whales, dolphins, crows, parrots, and apes, to name a few, have been shown to possess a high level of intelligence.
Then we wondered if it was our cocky-awareness that makes united states unique? Not quite. Apes show various degrees of self-sensation.
So, is it our communication skills? They are indeed highly developed only, over again, they are not unique. Whales, dolphins, birds, and apes all communicate via quite complex languages.
It has been suggested that our capacity to feel and show empathy is uniquely man. All the same, have you seen a mother elephant grieving over her dead infant? Or her whole herd commiserating with her? And, what well-nigh the African buffaloes who class a protective shield around a female who is giving nativity in order to ward off predators and vultures?
In short, nosotros are becoming increasingly aware that all these "man" traits started evolving millions of years before the offset human descended from the trees to take his first tentative steps in the African savannah. That being said, there are some characteristics of humans that are truly unique and different from "lower animals." Permit's explore some of them.
Our infrequent neurobiology allows usa to plan for the future
Daniel Gilbert points out in his bestseller "Stumbling on Happiness" that,
"The human is the only brute that thinks about the time to come."
Annotation also, that he adds a pregnant caveat, "…the long-term future."
Now, my domestic dog does seem to plan for the near hereafter (minutes from now). He stations himself past his food bowl nigh 9 AM when his breakfast time rolls around. And he starts to bark at me when it is time for his afternoon walk. But is he planning to ship his offspring to canis familiaris school? Of course not.
Does the silverback gorilla in the bulletproof forest of Uganda worry about the potential effect of global warming on the food supply for his troupe v years from now? Not that we know. In fact, experimental bear witness suggests that they don't.
Whatsoever looks like a long-term pre-planned activity in animals, like birds building a nest for the future chicks, is believed to exist the effect of genetically pre-determined, automatic behavior.
If we have the notion that we are only animals that plan for the futurity, then it begs the question:
What is the underlying genetic and neuronal basis for such a breathtaking jump from an animate being living in the present to i that is worried about the future and is planning for it?
As an extension of that, let me add together the observation that we are the just species that, as part of our awareness of the future, wonders about our part in the globe, and is concerned (frightened?) about dying one day.
The progress of evolution
Before we examine the changes in the brain that fabricated information technology possible for u.s. to plan for the future when our closest evolutionary cousins, the great apes, apparently cannot, let's accept a await at how evolution progresses.
Kelley Harris, now an Assistant Professor of Genome Sciences at the University of Washington studies the evolution of mutagenesis. That is, how genomes modify over time to produce variations in traits of humans and other animals, including some that allow new species to emerge.
The popular "molecular clock" model of natural selection posits that mutation rates evolve very slowly over, perhaps, tens of millions of years. This is the footing of the gradual quantitative accretion of mutations during evolutionary time.
For case, our biological clock and that of the lowly yeast are very similar. Yeast emerged about one.v billion years ago, archaic Homo evolved about 600,000 years agone. Modern H. sapiens almost 300,000 years agone. Remember of that, over a billion years and hardly any significant genetic change in that trait.
Harris's piece of work, however, demonstrates that Deoxyribonucleic acid replication fidelity is a lot like other biological traits, sometimes evolving at a snail'south step and sometimes evolving by leaps and premises for reasons that normally elude u.s..
The evolution of our brains
One could speculate, and so, that if at that place is a qualitative difference between us and our closest relatives, the gorillas, chimps, and bonobos, it must take been ane of those "leaps and premises" that Harris'south work demonstrated.
Merely why speculate? An international team of 38 scientists led by Nenad Sestan of Yale Academy published a magnificent achievement in the quest to understand what makes the human brain unique.
The investigators focused on 16 regions of the brains of adult humans, chimpanzees (ape), and macaques (monkey) involved in college-guild knowledge and behavior. They looked at the genetic information in the cells of these regions by sequencing the total mRNA of each cell. mRNA is the molecule that transcribes a gene from the Dna lawmaking into a poly peptide. The total population of a jail cell's mRNA is known as its transcriptome.
Then they went further. They overlaid the data of each prison cell'due south transcriptome on histological sections of these tissues. They did this so they could get an integrated picture of every jail cell in a tissue, including its genetic and protein content.
Human-specific cells
In addition to all kinds of variations in the molecular and cellular features between humans and chimpanzees, in that location was i finding that takes your breath abroad. They found some rare cells that are present in humans and are completely absent in chimpanzees and macaques.
These human being-specific cells are located in the striatum, a nucleus (an bunch) of neurons in the midbrain. The proper noun, striatum, comes from its appearance as stripes of grayness and white matter.
Some cells in the striatum are activated past the neurotransmitter dopamine. They are known as dopamine interneurons. Functionally, the dopaminergic (dopamine-responsive) striatum cells coordinate multiple aspects of knowledge, including motor- and activity-planning determination-making, motivation, reinforcement (which carried to an extreme tin can cease up in addiction), and reward perception.
The newly discovered human-specific cells (called dopamine interneurons) were found to secrete dopamine. And, these interneurons, in turn, activate the dopamine responsive neurons. Could it be that this is the location in the encephalon that makes us exceptionally, well…human? We just exercise not know however.
Some unanswered questions
There are all the same some of import unanswered questions:
- Exactly which cells in the striatum do those dopamine interneurons communicate with?
- What functions do these cells perform?
But Daniel Gilbert'due south observation that humans are the only animals that call back about the future may be getting a solid cellular and molecular footing. Although we don't still know if the anatomical finding and the psychological observation are at all related, these findings are withal, quite intriguing.
Anatomically, we are the only mammals that have this specific dopaminergic jail cell type. And nosotros are manifestly the only animal that engages in long-term planning.
But that isn't the only way in which we differ from other animals. Let'due south examine another fascinating way in which we are unique.
What on world is glycobiology?
In an article in Nature magazine, Bruce Lieberman reviewed the fascinating work of Ajit Varki of the University of California, San Diego. Dr. Varki is trying to uncover the mystery of human uniqueness. Now, if y'all guessed that Dr. Varki is a trained anthropologist, or a neurobiologist, or even a philosopher, I wouldn't blame you. These are the usual suspects in this field. But in actual fact, he is a glycobiologist. What'due south that anyway?
Glycobiology is the study of sugars in biology. Until quite recently, this field was the backwater of biochemical research. And why non? DNA could crow about its part in storing all our genetic information. RNA could merits to be the crucial span between the data stored in DNA and the formation of proteins. And proteins had bragging rights as the machinery of life, performing all the functions that are disquisitional for any living organism.
Only sugars? These molecules can be alone or monosaccharides, such as glucose or fructose, or tin form bondage called polysaccharides. But they are totally unglamorous. Glucose provides energy to the cell. Polysaccharides mainly embrace the cell surface. They are basically dumb molecules. They have none of the sophisticated functions of data storage or enzymatic activeness.
Now bear with me for a second, and don't get intimidated by the chemical terminology. You'll exist rewarded with an amazing insight.
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Vive la petite departure
N-acetylneuraminic acid (superlative) and North-glycolylneuraminic acid (bottom)
What kind of polysaccharides cover the prison cell surface? In humans, the most common is a blazon of sialic acid called N-acetylneuraminic acid or Neu5Ac.
Dr. Varki discovered that we are the only animal that has this molecule exclusively. All other animals have a dissimilar sialic acid on their jail cell surface, called N-glycolylneuraminic acid or Neu5Gc.
Look at the molecules. Y'all don't have to be a chemist to realize that the difference between u.s. and the residual of the brute kingdom is tiny—one oxygen molecule! (It'southward shown in blueish in the graphic.)
In fact, Varki institute that a mutation in the enzyme involved in the synthesis of Neu5Gc rendered it inactive. That's how nosotros humans concluded up with Neu5Ac. In a 2019 study published in the PNAS Varki'south grouping showed that this human-specific genetic mutation affecting cell-surface may be one other cistron.
They also show that the same mutation can help explain the apparently human-specific increased run a risk of CVD events associated with cerise meat consumption. Now, hither is a mutation that is non merely anthropologically intriguing, it probably of paramount importance in understanding our uniqueness in developing coronary artery disease that may exist related, in part, to the consumption of carmine meat.
One minor step in glycobiology, one giant step for humanity
How so? For that, we should inquire a question that is basic to evolution: Why did this mutation survive? What selective advantage did it confer on the newly minted humans compared to their ancient evolutionary cousins, the chimps and bonobos?
The respond is not known all the same, merely Varki points out a tantalizing clue. Humans are not susceptible to a type of malaria organism that afflicts our ancient ancestors the chimpanzees. That organism is Plasmodium reichenowi. This parasite attaches itself to the cell surface past binding to Neu5Gc and we don't have it – so nosotros don't go it.
On the other manus, chimpanzees are non susceptible to Plasmodium falciparum, the homo malaria organism. So the overall motion picture is becoming clear, a single mutation allowed us to escape from at least one devastating illness, and maybe more. This is an enormous selective advantage.
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No free lunch
But after all, we do get malaria, admitting from a different species (P. falciparum). Interestingly, genetic assay of this species shows that it evolved in Africa, aslope the evolving humans. Further, information technology accompanied the bands of early humans as they migrated out of Africa.
This is not the only disease that we caused by becoming human. Asthma is pretty unique to us, as is rheumatoid arthritis, and Alzheimer'due south, and Parkinson'due south. The list goes on and on.
Does the sialic acid mutation play a role in all those uniquely human diseases? We don't know nonetheless. But what we do know is that sialic acid, carpet the cell surface, is critical to interactions betwixt cells.
And such interactions are critical to the immune response, to communication between neurons, to hormones binding to their target cells, etc, etc. It would not be surprising to find this molecule in the middle of physiological and pathological processes that are, well, uniquely human.
So there you lot have information technology. One tiny difference in a single molecule, and what momentous consequences information technology has wrought.
The lesser line
Humans have always thought of themselves as exceptional and unique. Even so, some of our early ideas about our uniqueness take been debunked.
We are non the only animals that are intelligent and nosotros are not the only animals that can communicate with each other.
That beingness said, some amazing science has demonstrated that there are some intriguing ways in which our behavior and even our biochemistry have truly rendered united states of america one-of-a-kind.
Other stories near evolution: The Fascinating Case of the Hairy Penis
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Originally published on July 22, 2015, this story has been reviewed and updated past the writer for republication on October iv, 2019.
Dov Michaeli, MD, PhD
Dov Michaeli, M.D., Ph.D. (now retired) was a professor and basic science researcher at the University of California San Francisco. In addition to his clinical and research responsibilities, he also taught biochemistry to get-go-year medical students for many years.
During this time he was also the Editor of Lange Medical Publications, a company that adult and produced medical texts that were widely used by health professionals around the world.
He loves to write nigh the encephalon and human beliefs as well every bit translate noesis and complicated bones science concepts into entertainment for the rest of the states.
He somewhen left academia to enter the world of biotech. He served every bit the Principal Medical Officeholder of biotech companies, including Aphton Corporation. He also founded and served every bit the CEO of Madah Medica, an early-phase biotech company that adult products to improve post-surgical hurting control.
Now that he is retired, he enjoys working out for ii hours every mean solar day. He also follows the stock market place, travels the world, and, of class, writes for TDWI.
Source: https://thedoctorweighsin.com/humans-different-from-animals/
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