estimation of dates for the first living cells and LUCA Flashcards
What role does palaeontology play in estimating the age of the first cells and LUCA?
Palaeontology provides evidence through fossil records and geological studies to help estimate when the first living cells and LUCA (Last Universal Common Ancestor) appeared.
What is the earliest uncontested evidence of life?
The Strelley Pool Formation in Western Australia contains fossilised stromatolites dating back to 3.42 billion years ago (Gya), suggesting the earliest cells and LUCA existed around this time.
What is a stromatolite?
A stromatolite is a structure formed when cyanobacteria trap sediments and secrete calcium carbonate, building rocky mounds over time.
Why is 3.42 Gya a minimum date for the earliest cells and LUCA?
Stromatolites date back to 3.42 Gya, but simpler forms of life existed before stromatolite-forming bacteria, so the earliest cells and LUCA must have existed earlier than this.
What evidence can be found in metamorphosed rocks?
Metamorphosed rocks (altered by heat and pressure) do not contain clear fossils. However, isotope ratios, such as 13C/12C, can be used to indicate life.
What does the 13C/12C ratio tell us about ancient life?
Carbon from living organisms has a low 13C/12C ratio. Evidence of this ratio in banded iron rock from Greenland suggests life existed as early as 3.7–3.85 Gya.
Why don’t we find rocks older than 4.0 Gya on Earth?
Tectonic processes continuously destroy old rocks through subduction and form new rocks from magma, so rocks older than 4.0 Gya no longer exist.
What is the significance of zircon particles found in Western Australia?
Zircon particles with a depleted 13C/12C ratio were found in rocks dating back to 4.1 Gya, suggesting a biogenic origin, but this is not definitive proof of life.
How can genomic data help estimate the age of LUCA and the first living cells?
The number of genetic differences between two species is proportional to the time since they shared a common ancestor, allowing scientists to estimate the age of LUCA and early life.
When does recent research suggest LUCA and the first living cells existed?
Recent studies suggest that LUCA and the first living cells existed around 4.5 Gya, shortly after the Earth was impacted by the planet Theia, which formed the Moon.
