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July 15, 2015

How animal-like are humans

Scott Stockdale

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While both humans and animals are occupied with eating, sleeping, mating, and defending, humans can create a culture of their own, which becomes a kind of software of the human mind.

It automatically influences their courses of action. As human beings, we can question ourselves; we can build our vision, and make efforts to realize our vision; but animals do not have this competence.

Humans must remain in the care of their parents for much longer than other living primates.

The question then becomes why, when it might make more evolutionary sense to grow as fast as possible to have more offspring.

The explanation may be our brains, which presumably require a long time to grow and learn. However, it has been recognized that the physical characteristics of the human brain do not warrant the extreme creative and processing power that defines human ingenuity.

Most animals reproduce until they die, but in humans, females can survive long after ceasing reproduction. This might be due to the social bonds seen in humans — in extended families, grandparents can help ensure the success of their families long after they themselves can have children.

In terms of physiolog, there are many ways that the eyes of various animals are different from human eyes. They are different in size, shape, construction, light and colour sensitivity, purpose and function.

Very few animals have colour vision similar to humans. In fact only a few types of monkeys and fish seem to see colour like we do. However, some birds, insects, and shrimp can actually see more types of colour variation than we can. Most animals cannot see colour nearly as well as us.

The colours we see can be bright or dark, of different hues (e.g., red, yellow, green, blue, purple, etc.), and of different vividness (how much of the hue, or how different from neutral colours like white, black, or grey).

Animals see shades of grey and maybe another type of change in hue; much like someone with colour-blindness would. Cats, dogs, and other mammals fall into this category. But even though some of them can't see colour well, they can see much better than us at night.

Some animals, like cats, are nocturnal and their eyes are designed to be much more sensitive to light than ours. That helps them see when it is too dark for us to see much at all. Our colour vision lets us do things like identify good food and find it to feed ourselves.

Other animals need to see behind them in case a predator is trying to sneak up on them. Others have overlapping vision in the two eyes to better be able to locate objects in the world. That's very important for animals that move quickly, or fly through the world.

Our eyes are made much like a camera, with a lens, a pupil, and light-sensing cells in the back. Those eyes are great for land mammals and fish, but they are too large and complicated for other creatures, like insects, that have compound eyes.

Compound eyes have a whole bunch of individual lenses focused on different parts of the world. Each of those segments has a few light receptors, so they also don't get as much information about the world. Even stranger, some creatures, like lobsters, don't have lenses at all, but have mirrors to collect the light underwater.

It is known that various species of land and water-based living creatures are capable of hearing some lower and higher frequencies than humans are capable of detecting.

However, scientists from the Hebrew University of Jerusalem and elsewhere have now for the first time demonstrated how the reactions of single neurons give humans the capability of detecting fine differences in frequencies better than animals.

Experimental study of neural activity in the human auditory cortex has been limited until now to non-invasive techniques that gave only a crude picture of how the brain responds to sounds.

But recently, investigators from the Hebrew University, the University of California, Los Angeles (UCLA), the Tel Aviv Sourasky Medical Center and the Weizmann Institute of Science were successful in recording activity of single neurons in the auditory cortex while the subjects were presented with auditory stimuli.

They did this by utilizing an opportunity provided during an innovative and complicated clinical procedure, which traces abnormal neural activity in order to improve the success of surgical treatment of intractable epilepsy.

In tests measuring response to artificial sounds, the researchers found that neurons in the human auditory cortex responded to specific frequencies with unexpected precision.

Frequency differences as small as a quarter of a tone (in western music, the smallest interval is half a tone) could be reliably detected from individual responses of single neurons.

Such resolution exceeds that typically found in the auditory cortex of other mammalian species (besides, perhaps, bats, which make unique use of their auditory system), serving as a possible correlate of the finding that the human auditory system can discriminate between frequencies better than animals.

The result suggests that the neural representation of frequency in the human brain has unique features.

In terms of running speed, Olympic sprinter Usain Bolt ran 100 meters in 9.58 seconds compared with the 5.8 seconds it would take a cheetah to cover that same distance. Mr. Bolt ran 200 meters in 19.19 seconds, while a cheetah could sprint that distance in 6.9 seconds, a Black Caviar racehorse would gallop the same in 9.98 seconds, and a greyhound in 11.2 seconds.

Retired American sprinter and gold medalist Michael Johnson ran the 400 meters in 43.18 seconds: the greyhound 21.4 seconds: A racehorse 19.2 seconds. Kenyan runner David Rushida, world-record holder for the 800 meters, ran that distance in 1 minute, 41 seconds. That's compared with a 33-second time for the pronghorn antelope and 49.2 seconds for a greyhound.

World champ Mike Powell is known for his record-breaking jumps, reaching 29.36 feet (8.95 meters) in the long jump, but that's nothing for a red kangaroo, which can leap 41.99 feet (12.8 m).

The animal kingdom also has a strong contender for the high jump: The snakehead fish can leap 13 feet (4 m) out of the water, easily snatching the medal from athlete Javier Sotomayor, who jumps to 8 feet (2.45 m).

Even Olympic weightlifters would have to contend with some fierce competition from the African elephant, which can lift 661 pounds (300 kilograms) with its trunk and carry 1,807 pounds (820 kg), the grizzly bear, which can tote some 1,003 pounds (455 kg), and the gorilla, which can lift a whopping 1,984 pounds (900 kg).

Humans are able to hold their breath underwater and undertake rudimentary locomotive swimming within weeks of birth, as an evolutionary response.

Swimming has been recorded since prehistoric times, and the earliest records of swimming date back to Stone Age paintings from around 7,000 years ago.

Ten feet in length (3.05 metres) and 220 pounds (99.8 kilograms) the sailfish is considered the fastest swimmer, clocked at 68 miles per hour (30.4 metres per second).

In a pool for a 200 metre race, the fish would finish in less than ten seconds. For comparison, Olympic gold-medalist Michael Phelps swims the 200-metre freestyle in about 1.4 minutes, which translates to 4.7 miles per hour (2.1 metres per second).

Animals have hunger drives too. But when we observe other species in the wild, we seldom see fat animals.

There is a natural food (or foods) that is perfect for every animal. When that food is available they eat it. And somehow they eat exactly the right number of calories to keep them lean and healthy.

If every animal has a natural diet, there must be one for humans. For most of human history, the vast majority of people ate plants because they could not afford meat, or it was simply not available.

People had no overeating problem. They ate until they were satisfied and then they stopped eating. A generation ago, most people throughout Asia, Africa and Latin America ate plant foods and were healthy and slender.

The Chinese ate many whole plant foods and few animal foods. They were not overweight. They took in 33 grams of fiber a day, compared to a U.S. average of 12 grams. The Chinese diet contained only 14.5% of its calories from fat, compared to the American diet average of 34 - 38%. It is easy for our bodies to store dietary fat, and the process doesn't burn many calories.

In terms of body temperature, thermoregulation in organisms runs along a spectrum from endothermy to ectothermy.

Endotherms create most of their heat via metabolic processes, and are colloquially referred to as warm-blooded. Ectotherms use external sources of temperature to regulate their body temperatures. They are colloquially referred to as cold-blooded despite the fact that body temperatures often stay within the same temperature ranges as warm-blooded animals.

Most humans will suffer hyperthermia after 10 minutes in extremely humid, 140-degree-Fahrenheit (60-degrees-Celsius) heat. Death by cold is harder to delimit.

A person usually expires when their body temperature drops to 70 degrees F (21 degrees C), but how long this takes to happen depends on how "used to the cold" a person is, and whether a mysterious, latent form of hibernation sets in, which has been known to happen.

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