Iron has played an important role in the evolution of life on Earth, according to scientists.
Two Oxford University academics – Hal Drakesmith, a professor of iron biology, and Jon Wade, an assistant professor of planetary materials – have proposed that the abundance of iron on other worlds might suggest the possibility of sophisticated life.
Our crimson blood contains a lot of iron. We require iron for development and immunity. It is even added to meals like cereals to guarantee that enough of this mineral is present in the diet to prevent an iron shortage.
On a far smaller scale, the iron shortage may have aided evolution over billions of years throughout the evolution of life on Earth. Our new study, published in the Proceedings of the National Academy of Sciences (PNAS), suggests that rising and dropping iron levels on our planet may have allowed sophisticated species to emerge from simpler progenitors.
Our solar system’s terrestrial planets – Mercury, Venus, Earth, and Mars – contain varying levels of iron in their rocky mantles, the layer under the outermost planetary crust.
Mercury’s mantle has the least iron, whereas Mars’ contains the most. This oscillation is caused by variations in distance from the Sun. It’s also because of the different conditions under which the planets evolved their metallic, iron-rich cores.
The quantity of iron in the mantle controls various planetary processes, including surface water retention. And life as we know it cannot live without water. Astronomical surveys of other solar systems may allow estimations of a planet’s mantle iron, assisting in the hunt for planets capable of supporting life.
Iron is essential for the biochemistry that permits life to occur, as well as contributing to planetary habitability. Iron has a unique set of features, including the capacity to establish chemical bonds in numerous orientations and the simplicity with which one electron may be gained or lost.
As a result, iron mediates several biochemical processes in cells, particularly by facilitating catalysis – a mechanism that accelerates chemical reactions. Iron is required for key metabolic activities such as DNA synthesis and cellular energy production.
We calculated the quantity of iron in the Earth’s waters throughout billions of years in our research. We then explored the impact of massive amounts of iron descending from the seas on evolution.
The evolution of iron
More than 4 billion years ago, the first formative processes of geochemistry turned into biochemistry, and hence life, occurred. And everyone agrees that iron was a critical component in this process.
The circumstances on early Earth were very different from those that exist now. Because there was nearly no oxygen in the atmosphere, iron was easily soluble in water as “ferrous iron” (Fe2+). The availability of nourishing iron in the Earth’s early waters aided the evolution of life. This “ferrous paradise,” however, was not to last.
The Great Oxygenation Event caused oxygen to arrive in the Earth’s atmosphere. It began roughly 2.43 billion years ago. This altered the Earth’s surface and resulted in a significant loss of soluble iron from the planet’s upper ocean and surface waters.
The Neoproterozoic, a more recent “oxygenation episode,” happened between 800 and 500 million years ago. This increased oxygen concentrations even further. As a result of these two occurrences, oxygen mixed with iron and gigatonnes of oxidized, insoluble “ferric iron” (Fe3+) plummeted out of ocean waters, rendering most lifeforms inaccessible.
Life has grown – and continues to develop – an unavoidable need for iron. The lack of access to soluble iron has significant ramifications for the evolution of life on Earth. Behavior that maximized iron uptake and use would have had an obvious selective advantage. In today’s genetic research of infections, we can show that bacterial varieties that can efficiently scavenge iron from their hosts outperform less capable rivals over a few brief generations.
The “siderophore” – a tiny molecule generated by many bacteria that collects oxidized iron (Fe3+) – was a significant weapon in this war for iron. After oxygenation, siderophores became much more helpful, allowing organisms to ingest iron from minerals containing oxidized iron. Siderophores, on the other hand, aided in the theft of iron from other species, particularly bacteria.
This shift in emphasis, from getting iron from the environment to stealing it from other lifeforms, established a new competitive relationship between viruses and their victims.
As a result of this process, both parties’ strategies for attacking and defending their iron resources changed over time. This tremendous competitive drive resulted in progressively complicated behavior over millions of years, culminating in more evolved species.
Other techniques, other than thievery, can assist alleviate the reliance on a scarce resource. Symbiotic, cooperative interactions that share resources are one such example. Mitochondria are iron-rich, energy-producing devices that were formerly bacteria but now live in human cells.
a number of cells The ability of complex organisms to cluster together allows for more effective utilization of scarce nutrients than single-celled species such as bacteria. Humans, for example, recycle 25 times as much iron each day as we consume.
From an iron-biased perspective, infection, symbiosis, and multicellularity provided diverse but elegant ways for lifeforms to overcome iron constraints. The requirement for iron may have affected development, including modern life.
Earth highlights the significance of irony. The combination of an early Earth with physiologically accessible iron and the subsequent removal of iron via surface oxidation has resulted in unique environmental forces that have aided in the development of complex life from simpler antecedents.
These exact circumstances and changes over such long durations may be unusual in other worlds. As a result, the chance of encountering additionally evolved lifeforms in our cosmic neighborhood is likely to be minimal. Looking at the quantity of iron on other worlds, on the other hand, might help us locate such uncommon worlds.
Hal Drakesmith, University of Oxford Professor of Iron Biology, and Jon Wade, University of Oxford Associate Professor of Planetary Materials