Year: 2022

CALL FOR CORROBORATION. “The authors document the methodological and statistical criteria for these determinations and recommend that analogous investigations be conducted elsewhere.” https://www.sciencedirect.com/science/article/pii/S0012825219302636?via=ihub View in LinkedIn

MAGNETIC SHIELD AND CAMBRIAN EXPLOSION. “Organic evolution may have been enabled by geodynamic changes, particularly if the possible origin of Earth's strong dipolar magnetic field coincident with the origin of the asthenosphere and plate tectonics about 600 m.y. ago is valid.” https://www.sciencedirect.com/science/article/pii/S0012825219302636?via=ihub View in LinkedIn

EARLY PROKARYOTIC LIFE ON EARTH. “Life was present on Earth by 3.6 or 3.5 b.y. ago but until the latest Proterozoic, 3 b.y. later, it was limited to single-celled organisms. Early on these were only of prokaryotes whose cells lacked nuclei—bacteria, including photosynthetic (which released O2) and methanogenic types and Archaea—but they later included probable unicellular eukaryotes with nuclei.” https://www.sciencedirect.com/science/article/pii/S0012825219302636?via=ihub View in LinkedIn

LATER MULTICELLULAR LIFE. “Soft-bodied multicellular organisms first appeared about 600 m.y. ago. During Ediacarian time (from then until about 540 m.y.) these are known only as soft-sediment impressions of unclear taxonomy and even whether they were plants or extremely primitive animals is unknown.” https://www.sciencedirect.com/science/article/pii/S0012825219302636?via=ihub View in LinkedIn

THE CAMBRIAN EXPLOSION. “Then came the Cambrian explosion of evolution, starting about 540 m.y. ago, and within about 50 m.y. most of the phyla of modern animals had been generated including the chordates to which we belong. Some animals were a meter long.” https://www.sciencedirect.com/science/article/pii/S0012825219302636?via=ihub View in LinkedIn

CONTENTIOUS STORY. “The causes of evolution across those two great thresholds, about 600 and 540 m.y. ago, have been subjects of much debate.” https://www.sciencedirect.com/science/article/pii/S0012825219302636?via=ihub View in LinkedIn

COSMIC RADIATION. “One prerequisite is that two types of incoming radiation must have been largely blocked to allow profusely varied life forms to exist on Earth's surface. One of the lethal radiation types consists of cosmic rays (high-energy ionized particles from the Sun and from outside the Solar System) which are now mostly blocked from the surface by Earth's internally generated strong dipolar magnetic field.” https://www.sciencedirect.com/science/article/pii/S0012825219302636?via=ihub View in LinkedIn

UV RADIATION. “The other lethal radiation is the high-energy fraction of ultraviolet light (short-wavelength UVB and shorter UVC) in the short-wavelength tail of solar radiation that consists mostly of visible light. UVB is mostly absorbed by a diffuse layer of ozone (O3) in the stratosphere and UVC is scattered to harmlessness by O2 and N2 molecules (which makes Earth's sky appear blue).” https://www.sciencedirect.com/science/article/pii/S0012825219302636?via=ihub View in LinkedIn

MAGNETIC RADIATION SHIELD. “Atmospheric oxygen is known to have been increasing in the relevant era but this is poorly quantified. A newly-formed, weak dipolar magnetic field originating about 600 m.y. ago, strengthening at about 550 m.y., could plausibly have shielded against ionized radiation, enabling the Ediacarian start and Cambrian acceleration of multicellular evolution.” https://www.sciencedirect.com/science/article/pii/S0012825219302636?via=ihub View in LinkedIn

PROKARYOTIC RESISTANCE TO RADIATION. “There is an enormous range in resistance to ionized radiation among modern unicellular life forms, including prokaryotes, which Sharma et al. (2017) showed to correlate with Mn2+ ions in antioxidant complexes within cells. This idea can perhaps be tested directly by analysis of cellular residues in Precambrian rocks.” https://www.sciencedirect.com/science/article/pii/S0012825219302636?via=ihub View in LinkedIn