Isegoria

In Suspending Life, Peter Ward notes that almost every species on Earth was killed 250 million years ago:

By about 251 million years ago, the planet had lost all of its ice, and with the final glaciers melting away, there was no longer a sufficient heat difference between the tropics and poles to maintain the various ocean currents that had kept the waters both cold and oxygenated. Stagnation ensued as the currents slowed; the ocean bottoms lost their oxygen and sea animals died. With this shift in ocean chemistry and temperature, new microbes that thrive without oxygen bloomed into dominance and rapidly reproduced to ocean-filling numbers. Some of these microbes were relatively benign to the life on Earth that does depend on oxygen, but some produced toxins such as those found now in red tides. A few others produced something even worse — hydrogen sulfide.

The oceans became much like the modern Black Sea, with warm, deep, oxygen-less water masses covering the bottom and oxygenated regions at the surface. Slowly yet inexorably, the warming oceans began to bring oxygen-less bottom waters toward the surface. By the time this process was complete, the microbes producing hydrogen sulfide were able to live at every depth. Vast new suites of other microbes appeared, belonging to the purple and green sulfur bacteria groups that require both hydrogen sulfide in the water around them and sunlight to run their photosynthetic pathways. These microbes took over in the oxygen-free water, rich in poisonous H₂S and shallow enough to provide sufficient light for energy.

What I believe happened next still reverberates through life’s history. The H₂S-producing microbes eventually grew to such numbers that the toxic byproduct of their metabolism could no longer be contained in seawater solution. Large oily bubbles of hydrogen sulfide came out of the purple-stained sea and entered the atmosphere, where the gas increased in concentration to levels that surely had destructive effects. Where the H₂S was concentrated at more than 200 ppm, it was toxic to both plants and animals. But more globally, H₂S began to break down the Earth’s protective ozone layer, allowing harmful ultraviolet light to enter.

The fossil record shows us that at this point, the most catastrophic mass extinction in Earth’s history occurred. Claims that this “great dying” was caused by the effects of an asteroid from space, just like what killed the dinosaurs, simply don’t hold up. Almost everywhere we find biomarkers indicating that there existed an oxygen-free, toxic ocean — and that on land, almost all plants and animals quickly died out.

Here’s where it gets odd, because hydrogen sulfide isn’t all bad — at least not for those of us who descended from the animals that survived that cataclysm:

While high levels of H₂S kill mammals, Roth’s team has found that very low levels of the toxin can prolong their lives. H₂S reduces oxygen levels in the body, and though too much causes death by oxygen starvation, a bit less slows a creature’s metabolism. This alone is an amazing finding. But Roth has gone further, inducing suspended animation in mammals. By exposing lab mice to small doses of H₂S, Roth and his team can put them into the deepest of sleeps — with very slow, or even no heartbeats — for several hours. In that time, the mice can be cooled to temperatures that would have killed them prior to the H₂S exposure.

Roth has already begun testing his work on other mammals. If he is correct, hydrogen sulfide may provide a way of saving lives so revolutionary that it will change trauma medicine forever. He is redefining what we thought we knew about death and dying. Death may not be as final as we think.

When we humans are cut or injured, our bodies naturally produce small quantities of hydrogen sulfide. In essence, the body may be trying to put itself into suspended animation to survive the injury, an instinct held over millions of years in our genes. Yet whenever one of us is dying, say from a heart attack, our first instinct is to give that person oxygen. The problem with this “life-saving” first response may be that the oxygenated red blood cells rush to the damaged cells and act like gasoline on a fire. Oxygen is one of the most chemically active substances on Earth, and though we need it to survive, it can ravage our bodies. The oxygen increases the reactions causing the heart attack in the first place; it tears up more cells and overwhelms the virtual suspended animation that the body-produced hydrogen sulfide created. Then it kills you.

Perhaps our first instinct in instances of a heart attack should be to cool the body and let hydrogen sulfide do its natural work. To save life, in other words, you may first have to effectively suspend it with hydrogen sulfide. This tactic may just be what got us so far in the first place.

Vitamins 'may shorten your life':

The trials involved 233,000 people who were either sick or were healthy and taking supplements for disease prevention.

After various factors were taken into account and a further 20 studies excluded, the researchers linked vitamin A supplements to a 16% increased risk of dying, beta-carotene to a 7% increased risk and vitamin E to a 4% increased risk.

Vitamin C did not appear to have any effect one way or the other, and the team said more work was needed into this supplement — as well as into selenium.

In conclusion, “we found no evidence to support antioxidant supplements for primary or secondary prevention,” they said.

It was unclear exactly why the supplements could have this effect, but the team speculated that they could interfere with how the body works: beta-carotene, for instance, is thought to change the way a body uses fats.