Desertborn Physiological Adaptations to the Desert

 

Desertborn Physiological Adaptations to the Desert.

2887 years ago, Devotees of the Tau from various parts of the Trantorian Imperium emigrated to a desolate desert planet Araxes. They arrived on Araxes as Tauists, over the generations they became Araxi, and sometime during the following 115 generations their physiology adapted to become what is now referred to as the Desertborn.

Humani Araxi (Homo Sapiens Sapiens Araxi) are technically near-baseline humani, and are 100% interfertile with baseline humani as well as other near baseline humani variants. The Desertborn genome diverged from the baseline humani genome many scores of generations ago, but not so divergent that they would no longer be classified as human. Except for the nucleated blood, there is no adaption of the Desertborn genome which is not a naturally occurring variant in the baseline humani genome. Even the nucleated blood is very similar to the blood of baseline humani afflicted with sickle cell anemia.

There are several well known aspects of Desertborn physiology: Their extremely efficient endocrine system and immunological system, their overall health, rapid recovery, and the longevity that results; plus some sensory and cognitive enhancements appear. These physiological and cognitive adaptation are related to the influence of the Araxes Spice and are the subject of a different article. Here, we are only speaking to the physiological adaptions of the Desertborn which result from genetic level changes, presumably by natural, sexual, and cultural selection.

Any desert dwelling species has to deal with two conflicting survival issues, water conservation and cooling.

Desertborn are fundamentally humani based stock and are designed for excess cooling which expends a great deal of water. To bio-engineer changing that cooling/water management would be so drastic that the result would be that they are no longer be humani.

The iconic environment suit of the Desertborn is a technological means of dealing with the water loss from the cooling apparatus of the humani body, which would be unreasonable to re-engineer and unlikely to come about via natural selections.

There are millions of genetic variations on even a relatively small population like the Araxes Desertborn, and not all of the adaption for the low air pressure, low oxygen content, hot and dry climate of Araxes are shared equally. Especially due to the relatively small but near continual introduction of offworlders via marriage, some adaptations are more common than others. The overall population is large enough that we no longer requires marriage to offworlders to keep the genetic diversity viable, but the practice continues.

The low atmospheric pressure (thin air) and low oxygen content of the Araxes atmosphere, albeit higher than during colonization era, still requires unadapted offworlders to have oxygen support except when in the lowlands of the border and north.

The thin air and low oxygen content of the Araxes atmosphere resulted in similar adaptation of humans who have acquired the ability to survive at extremely high altitudes. These adaptations are irreversible, long-term physiological responses to high-altitude environments, associated with heritable physiological and genetic changes, not just temporary acclimation to moderate changes in the climate.

The most common adaptation to the thin air and low oxygen content is mostly extensive physiological and genetic changes, particularly in the regulatory systems of oxygen respiration and blood circulation. Mainstream humani populations would normally suffer symptoms similar to altitude sickness under the same conditions, often resulting in life-threatening trauma and even death without technological aids or medical assistance.

This special adaptation was a case of rapid natural selection in action during the early colonization era. The adaptation account of the Desertborn is one of the fastest cases of natural humani evolution on the scientific record, as some adaptations are estimated to have occurred in less than 1,000 years, others over 2800 years. There is some conjecture that the ambient Spice content of Araxes may have played a hand in the rapid adaptation rate. Scholars have researched, studied and debated about that since long before I was born and will likely continue to long after my time is past.

Mainstream Humani are naturally adapted to lowland environment where oxygen is abundant, typically 21% oxygen and 5 kilograms per square centimetre air pressure. Referred to as the Blue Zones (but also tolerable with time in the so-called Green Zone). When atmospheric pressure is below 75% of that normal, mainstream humani experience a type of hypoxia, a clinical syndrome of severe lack of oxygen. Complications include fatigue, dizziness, breathlessness, headaches, insomnia, malaise, nausea, vomiting, body pain, loss of appetite, ear-ringing, blistering and purpling of the hands and feet, and dilated veins.

The sickness is compounded by related symptoms such as cerebral oedema (swelling of brain) and pulmonary oedema (fluid accumulation in lungs). For several days, they breathe excessively and burn extra energy even when the body is relaxed, this results in a higher overall metabolism. The heart rate gradually decreases. In women, pregnancy can be severely affected, such as development of high blood pressure, called preeclampsia, which causes premature labour, low birth weight of babies, and often complicated with profuse bleeding, seizures, and death of the mother.

75% atmospheric pressure is the standard air pressure in the equatorial lowland borderlands in Araxes, which is probably not coincidentally where the majority of offworlders congregate. Even then, most require several days to several weeks to adjust to the low atmospheric pressure and low oxygen content.

The oxygen level in the southern hemisphere (the Australis) is about 60% of Mainstream Humani Standard, and     as low as 45% in parts of the southern highlands.

The air in the near southern hemisphere polar latitudes are much thinner. It the high altitude low latitude zone of the deep Australis, atmospheric pressure is a third of Humani Standard, most offworlders cannot breathe without technological assistance (oxygen masks). Hypoxia symptoms are more severe.

Polar latitudes have less radiation issues, within 15 degrees of the poles, the radiation is Terran standard normal.

Desertborn skin, eye colour, fat, hair, and nose.

Without much surprise, the Araxes climate strongly favours darker skin and eyes, but due to a regular influx of marriage with offworlders over the past 3000 years, there is still the introduction of genes for lighter skin and eye colours.

There are no dedicated genes which determine eyes colour, there are 22 different genes which do various things, which has the side effect of determining eye colour while they are determining various effects. Imperial technology can determine a lot about you from a sufficiently detailed picture of your eyes.

Light coloured eyes are more susceptible to radiation damage and more susceptible to losing flexibility too, both of which are strongly selected against in the Araxes environment.

Desertborn vision is adapted towards twilight conditions, visibly evident from slightly enlarged irises.

Larger eyes and even larger irises allow for both increased ability to work in low light as well as increased flexibility in response. Heavier birthweight makes larger eyes easier.

Larger irises with stronger and faster reaction to light differences evolved for working more in dawn and dusk conditions that were safer from radiation. The increase in retinal receptors improved night vision.

Desertborn skin has adapted to resist radiation induced cancers, mostly by being darker and thicker. The skin is lightly modified for a slight reduction in water loss, but there are limits without reducing the ability to cool the body.

While it is common for native Araxi to criticize others for being 'water fat', some Desertborn have fatty deposits that serve as both a food and water source when the going gets tough. Some of this manifests as a thick subdermal layer of fat, sometimes as fatty deposits in the posterior and abdominal area. Dehydration based ketosis makes for these fatty deposits to be more readily converted as an energy source. As such they are slightly less susceptible to bruising.

The subdermal fat layer provides moderate resistance to the rapid change from extreme daytime heat (120F 50C) to near freezing night-time temperatures.

The extra dermal layers also makes for a minor adaption of adjusting the proximity of the blood vessels from the surface of the skin to aid in resisting extreme heat or cold as needed. This added resistance to extremes of heat or cold is not substantial, but percentages often make the difference between life and death, or thriving versus merely surviving.

Some Desertborn have thicker hairs in their ears for keeping out sand, much more common is the thicker eyelashes which help to keep sand and dust out of the eyes. Despite its known usefulness, it is not considered aesthetically pleasing as it becomes overgrown with age.

Some Desertborn have closable nostrils to keep sand out, but more narrow nostrils are more common. Closable nostrils are about as common as being able to wiggling one’s ears.

A more common but not universal adaptation is the higher bridged thinner nose shape that humidifies breathed-in air. The larger nose were adaptations to moisturize the air breathed in, but also to warm the air breathed in, given daily temperature swings of sometimes more than 50 degrees between day and night the larger hawklike nose became more common.

There is a very strong tendency towards darker, thicker and wavier hair, and a stronger tendency away from straighter. finer hair such as is found in colder more humid climates.

Desertborn Heart, Lungs, Spleen, and Physical Maturity Rates

Desertborn have developmentally acquired enlarged residual lung volume and its associated increase in alveolar area which are supplemented with increased tissue thickness and moderate increase in red blood cells. Although the physical growth in body size is delayed until later puberty, growth in lung volumes is accelerated.

Larger lungs requires somewhat less moisture to function well enough.

Although not immediately obvious, the average Desertborn rib cage is slightly larger (much like opera singers are pictured to have) to accommodate the larger lung capacity and larger lung expansion.

The altered morphology of the Desertborn lungs and heart, allowing more efficient gas exchange and delivery, in particular the lungs have more capillaries, and their hearts have a heavier right ventricle which pumps blood to the lungs.

Desertborn have high levels (about double) of nitric oxide in their blood which helps blood vessels dilate for enhanced blood circulation.

Many Desertborn possess an enlarged spleen which provides a larger amount of oxygen-rich red blood cells.

A well documented but poorly understood phenomena, instead of reaching physical maturity between the ages of 15 and 18, a large portion of Desertborn reach physical maturity between 20 and 27, although cognitive maturity occurs at the usual mainstream humani age spread. Emotional maturity, like all humani subspecies is quite variable.

Desertborn Blood

In mainstream Humani immune systems, normally Y-shaped antibody molecules consist of two heavy (long) chains along the length of the Y, and two light (short) chains at each tip of the Y. In addition to these, Desertborn also have antibodies made of only two heavy chains, a trait that makes them smaller and more durable.

The most common shared adaptation of the Desertborn is elevated haemoglobin concentrations to cope with oxygen deficiency, and increased oxygen level in their haemoglobin. Desertborn also inhale more air with each breath, breathe more rapidly, and absorb oxygen more efficiently. Desertborn have better oxygenation at birth, sustained increase in cerebral blood flow and enlarged lung and heart volumes throughout life. Although respiration rates and inhalation volumes are increased, resting heart rates and blood pressure is reduced compared to mainstream humani.

At a glance, under a microscope, the most obviously difference is the blood cell's average smaller size, more variability of in size and are oval shaped rather than circular.

One of the more unusual Desertborn adaptations is the oval shaped red blood cells, instead of the round biconcave disks of mainstream humani populations. Most mainstream humani population red blood cells are typically shaped as biconcave disks: flattened and depressed in the centre, with a dumbbell-shaped cross section, and a torus-shaped rim on the edge of the disk. The biconcave shape optimizes the flow properties of blood in the large vessels, such as maximization of laminar flow and minimization of platelet scatter, which suppresses their atherogenic activity in those large vessels.

The oval shape of the Desertborn red blood cells allows their blood cells to expand up to 240% of its original volume, whereas the red blood cells of mainstream humani can only expand up to 100%. This allows the average Desertborn to store the equivalent of up to 8 litres of water in its bloodstream to recover from dehydration, three times that of mainstream humani. The elongated shape of Desertborn red blood cells allows for a higher affinity for oxygen.

The elongated shape of Desertborn red blood cells allows ease of travelling of thick blood thru narrow blood vessels during dehydration. One of the major issues of dehydration is blood sludging, unable to get thru smaller capillaries causing cellular damage from oxygen deprivation and other deprivation and the inability to flush out waste products. The average smaller shape, higher nitric oxide content which helps blood vessels dilate, and the oval shape allows the Desertborn blood to flow even when extremely dehydrated, minimizing cellular damage which would result from deprivation.

Desertborn can go days without drinking water, surviving extreme dehydration and safely losing up to a third of their body weight in water.

Even after severe dehydration, a Desertborn is able to drink massive amounts of water sometimes in just one session to make up the deficit; this amount of water would cause severe osmotic problems in mainstream humani. In the Desertborn, the water is absorbed from the stomach and intestines more slowly, allowing equilibrium to be established.

The Desertborn Spleen and Bone Marrow produce blood at a faster rate than mainstream humani. These and other adaptations such as higher metabolism and respiration result in a higher calorie, iron and protein intake rate than mainstream humani.

The pink colour of Desertborn breastmilk is caused by its high blood content, a side effect of the larger blood production in the bone marrow and the larger spleen. Please note that it is a capital offense to extract blood or breastmilk without the expressed uncoerced consent of the donor. It is also illegal to sell or distribute blood or breastmilk or bone marrow in the Mu Draconis System. Penalties are severe and juries tend to be especially unforgiving in this regard.