The article was published at The Conversation.
Hal Drakesmith is a professor at the University of Oxford.
Jon Wade is an associate professor at the University of Oxford.
Our red blood has a lot of iron. We need iron for growth and immunity. It is added to cereals to make sure there is enough iron in the diet to prevent iron deficiency.
Iron deficiency may have stimulated evolution on a very different scale than it has on Earth. Our new research shows that rising and falling iron levels on our planet may have enabled complex organisms to evolve from simpler forebears.
Mercury, Venus, Earth and Mars have different amounts of iron in their rocky mantles. Mercury has less iron than Mars. There are differences in distance from the sun. It is due to the different conditions under which the planets formed their metallic, iron-rich cores.
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Retention of surface water is regulated by the amount of iron in the mantle. Life as we know it cannot exist without water. Estimates of a planet's mantle iron can be made using observations of other solar systems.
Iron contributes to planetary habitability as well as the biochemistry that allows life to happen. Iron has a number of unique properties, including the ability to form chemical bonds in multiple orientations and relative ease of gaining or losing one electron. Iron is able to speed up chemical reactions by enabling catalysis, a process that speeds up chemical reactions. Iron is used in vital processes such as DNA synthesis and cellular energy generation.
We calculated the amount of iron in the seas over billions of years. The effect on evolution of iron falling out of the seas was considered.
Through the ages.
More than 4 billion years ago, the first formative events of life took place. There is a consensus that iron was the most important element in this process. The conditions of early Earth were very different to what we are experiencing today. The lack of oxygen in the atmosphere meant that iron was easily dissolved in water as "ferrous iron" Life evolved because of the abundance of iron in the early seas. The "ferrous paradise" was not to last.
Oxygen appeared in the Earth's atmosphere during the Great Oxygenation event. It happened around 2.43 billion years ago. The iron from the upper ocean and the surface waters of the planet was lost. Between 800 to 500 million years ago, there was a secondoxygenation event. This increased the oxygen concentrations. Oxygen and iron dropped out of ocean waters as a result of the two events.
Life has an inescapable dependency on iron. The evolution of life on Earth was affected by the loss of access to iron. The behavior that maximized the use of iron would have had a clear advantage. In genetic analysis of infections, we can still see that the more efficient the variant, the better it is for the host.
The "siderophore" is a small molecule produced by manybacteria that captures iron. After oxygenation, siderophores became more useful, allowing organisms to take iron from minerals. Siderophores helped steal iron from other organisms. The switch from acquiring iron from the environment to stealing it from other lifeforms set up a new dynamic of competitive interaction between pathogens and their hosts. Both parties evolved to defend their iron resources thanks to this process. More advanced organisms were created due to the powerful competitive drive.
Other strategies, besides theft, can help deal with the dependency. Cooperative relationships that share resources are an example. Mitochondria are machines that were originallybacteria and now reside in our cells. Multiple cells clumping together as complex organisms enable more efficient use of rare nutrients than single-celled organisms. Humans recycle 25 times more iron than we do from our diet. Lifeforms could counteract the limitation of iron by using different but elegant means. Life as we know it today may have been shaped by the need for iron.
Being ironic is important. The combination of an early Earth with biologically accessible iron and the subsequent removal of iron during surface oxidation has provided unique environmental pressures facilitating the evolution of complex life from simpler precursors.
These sets of conditions and changes are not usually found on other planets. The chances of other advanced lifeforms being found in our neighborhood may be low. Looking at the iron abundance on other worlds could help us find rare worlds.
The Conversation's article is a Creative Commons licensed one. The original article can be found here.
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