POLYPLOID PLANTS FAST EVOLUTION
During Cataclysmic Events
I read long ago that many domesticated plants were polyploid, having more than one set of DNA chromosomes. This finding was considered amazing and maybe miraculous or due to advanced ancient civilization. But then it was apparently discovered that stress causes polyploidy. Guess what caused stress.
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PLANT STRESS AS IN CATACLYSMS CAUSES POLYPLOIDY
OUR POLYPLOID CROPS
Many of the world’s most important domesticated crops are polyploid, meaning they have more than two sets of chromosomes. Common examples include:
Wheat: Modern bread wheat (Triticum aestivum) is hexaploid (six sets of chromosomes).
Strawberry: Cultivated strawberries (Fragaria × ananassa) are octoploid (eight sets).
Potato: Most cultivated potatoes (Solanum tuberosum) are tetraploid (four sets).
Cotton: Many commercial cotton species are tetraploid.
Banana: Edible bananas are typically triploid, which makes them seedless.
Canola: Canola (Brassica napus) is an allotetraploid.
Peanut: Peanuts are allotetraploid.
Sugarcane: Most varieties are highly polyploid.
Benefits of Polyploidy in Crops
Polyploidy provides several advantages that have been crucial for agriculture:
Increased Size and Vigor: Polyploid crops often have larger fruits, seeds, or tubers, and more robust growth.
Greater Genetic Diversity: Multiple chromosome sets allow for more gene variants, enhancing adaptability and resilience.
Disease and Stress Tolerance: Polyploids can better withstand diseases, pests, and harsh environmental conditions.
Seedlessness: Triploidy in crops like bananas and watermelons leads to seedless fruit, which is preferred by consumers.
Hybrid Vigor: Polyploidy can combine beneficial traits from different species or varieties, resulting in superior hybrids.
PLANT STRESS AS IN CATACLYSMS CAUSES POLYPLOIDY
Global cataclysms—such as asteroid impacts, massive volcanic eruptions, or abrupt climate shifts—can dramatically alter the environment:
Abrupt Temperature Changes: Sudden cooling or warming stresses plant metabolism and reproduction.
Prolonged Darkness or Reduced Sunlight: Impacts photosynthesis and growth.
Drought or Flooding: Disrupts water availability and nutrient uptake.
Increased Salinity or Pollutants: From ash, dust, or chemical fallout, can poison or stress plants.
Physical Damage: Widespread destruction from shockwaves, debris, or fire.
How Stress Produces Polyploidy
Stressful conditions disrupt normal cell division, especially during reproduction. This can cause:
Formation of Unreduced Gametes: Stress interferes with meiosis, leading to gametes (egg or pollen cells) that retain the full set of chromosomes instead of halving them.
Fusion of Unreduced Gametes: When these gametes combine, they produce offspring with doubled (or more) chromosome sets—polyploidy.
Selective Advantage: Polyploid individuals may be better equipped to survive and reproduce in the new, stressful environment, leading to their persistence and spread.
In summary, many domesticated crops are polyploid, which makes them more productive and resilient for human use. Cataclysmic events can stress plant populations, causing errors in cell division that lead to polyploidy. This process, in turn, can help plants adapt and thrive in challenging conditions.
YOUNGER DRYAS STRESSES
During the Younger Dryas, plants would have been subjected to a suite of severe and rapidly changing environmental stresses that are known to promote polyploidy. Here’s how those stresses break down and their relevance to polyploidization:
Major Stresses During the Younger Dryas
Abrupt and Severe Cooling: The Younger Dryas was marked by a dramatic and rapid return to near-glacial conditions, with temperature drops of 5–10°C in the North Atlantic region within just a few decades3,6,7. Such intense cold disrupts plant metabolism and reproduction, and is a well-documented trigger for errors in meiosis that can produce unreduced gametes, leading to polyploidy.
Rapid Climate Oscillations: The transition into and out of the Younger Dryas involved not just cooling but also rapid warming, creating highly unstable climate regimes1,6,7. These oscillations impose physiological stress on plants, which can further destabilize cellular division.
Glacial Advance and Retreat: The period saw glaciers regrow and then retreat, repeatedly disturbing soils, uprooting vegetation, and causing physical damage to plants and seeds3,6. Physical damage is another known trigger for meiotic errors and polyploid formation.
Drought and Aridity: The cold period led to increased aridity in many regions, reducing water availability and further stressing plant communities4,6. Drought is a classic inducer of polyploidy through its impact on cell division and gamete formation.
Shifts in Precipitation Patterns: Some regions experienced increased rainfall, while others became drier, forcing rapid shifts in vegetation zones and exposing plants to unfamiliar conditions6. Such environmental instability can promote polyploidization.
Catastrophic Disturbances: If the Younger Dryas was triggered or compounded by extraterrestrial impacts, as some evidence suggests, this would have added direct physical and chemical stresses—such as wildfires, atmospheric dust, and possibly increased soil and water salinity from fallout4,5,6. These factors can cause both direct damage and long-term environmental stress, both of which are linked to polyploidy induction.
How These Stresses Produce Polyploidy
Disruption of Meiosis: Extreme cold, drought, and physical damage interfere with the normal process of meiosis, leading to the formation of unreduced gametes (gametes with a full set of chromosomes rather than half). When such gametes fuse, they produce polyploid offspring.
Selective Advantage: Polyploid plants often have greater resilience to harsh conditions, so those that became polyploid during the Younger Dryas would have had a survival advantage, promoting the establishment of polyploid lineages.
Environmental Instability: Rapid environmental changes increase the likelihood of reproductive errors, which are the root cause of most natural polyploidy events in plants.
YOUNDER DRYAS COSMIC RAYS
It is plausible that the Younger Dryas period saw increased cosmic ray activity, especially if a cosmic impact or airburst event occurred as some evidence suggests. Multiple studies report proxies for such an event, including elevated levels of platinum, iridium, nanodiamonds, and meltglass in the Younger Dryas boundary layer across several continents2,3,4,5,6,7. These markers are consistent with a major cosmic impact or airburst, which would have temporarily increased the influx of cosmic rays and other extraterrestrial particles into Earth's atmosphere.
Would Increased Cosmic Rays Contribute to Polyploidy?
Cosmic rays are high-energy particles from space that, when they strike Earth's atmosphere, generate secondary radiation capable of penetrating living tissues. This radiation can cause mutations by breaking DNA strands or interfering with cell division. In plants, exposure to increased radiation—including cosmic rays—can:
Cause chromosome breaks or mis-segregation during cell division.
Induce the formation of unreduced gametes (gametes with a full set of chromosomes).
Lead to polyploidy if these gametes fuse to form viable offspring with doubled (or more) chromosome sets.
While the primary triggers for polyploidy in plants are usually environmental stresses like cold, drought, or physical damage, increased radiation from cosmic rays is a recognized mutagenic factor and could, in theory, contribute to polyploidization—especially if the radiation dose is high enough to disrupt normal meiotic processes.
In another recent post MAMMALS EVOLVED DURING FLOOD I pointed out evidence that mammals evolved rapidly during the Great Flood, due to a stronger electric field. I don’t know of such evidence for rapid evolution during the Younger Dryas, but that would also be possible, maybe to a lesser extent than during the Flood. Apparently, plants can “evolve” rapidly by both means, but animals “evolve” more by increased electric fields.