Scientists discover why fish evolved limbs and left water

Researchers find a key clue to the evolution of bony fish and tetrapods.

Scientists discover why fish evolved limbs and left water

Fish and tetrapods.

Credit: Karen Carr © The Field Museum
  • A new study says solar and lunar tide impacts led to the evolution of bony fish and tetrapods.
  • The scientists show that tides created tidal pools, stranding fish and forcing them to get out of the water.
  • The researchers ran computer simulations to get their results.

Tides influenced by the sun and the moon were likely the reason why fish developed limbs and early tetrapods evolved, found new research.

The groundbreaking study took a look at tides during the Late Silurian—Devonian periods, which happened between 420 million years ago and 380 million years ago.

The scientists built their work on the theory that the Moon's mass and specific location along its orbit can greatly affect vast tidal ranges across Earth and can create tidal pools. Because they are isolated from each other, the pools provided the biological motivation for fish stranded by high tides to eventually grow limbs.

The study involved researchers from UK's Bangor University and Oxford University as well as Uppsala University in Sweden. They devised very detailed numerical simulations that proved the existence of large tides during the period they studied. They are first to tie tidal hydrodynamics to an evolutionary biological event, states the press release from the University of Oxford.

To come up with the simulations, the scientists employed paleogeography, the study of historical geography, to reconstruct the Earth's continents within the numerical model. The calculations showed tides over four meters happening around the South China block. That area holds the known origin site of the earliest bony fish we know and has been a treasure-trove of the earliest fossils of that nature. Geological evidence also supports changes in tides to be lined to these fossils.

Neil deGrasse Tyson Explains the Tides

"Large tidal ranges could have fostered both the evolution of air-breathing organs in osteichthyans to facilitate breathing in oxygen-depleted tidal pools, and the development of weight-bearing tetrapod limbs to aid navigation within the intertidal zones," states the paper.

The researchers believe further tidal simulations from early Earth can be used to recreate that far past with greater detail. The findings can help us understand more what roles tides played in diversifying early vertebrates or in causing extinction events.

Check out the study published in Proceedings of the Royal Society A.


U.S. Navy controls inventions that claim to change "fabric of reality"

Inventions with revolutionary potential made by a mysterious aerospace engineer for the U.S. Navy come to light.

U.S. Navy ships

Credit: Getty Images
Surprising Science
  • U.S. Navy holds patents for enigmatic inventions by aerospace engineer Dr. Salvatore Pais.
  • Pais came up with technology that can "engineer" reality, devising an ultrafast craft, a fusion reactor, and more.
  • While mostly theoretical at this point, the inventions could transform energy, space, and military sectors.
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Why so gassy? Mysterious methane detected on Saturn’s moon

Scientists do not know what is causing the overabundance of the gas.

An impression of NASA's Cassini spacecraft flying through a water plume on the surface of Saturn's moon Enceladus.

Credit: NASA
Surprising Science
  • A new study looked to understand the source of methane on Saturn's moon Enceladus.
  • The scientists used computer models with data from the Cassini spacecraft.
  • The explanation could lie in alien organisms or non-biological processes.
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CRISPR therapy cures first genetic disorder inside the body

It marks a breakthrough in using gene editing to treat diseases.

Credit: National Cancer Institute via Unsplash
Technology & Innovation

This article was originally published by our sister site, Freethink.

For the first time, researchers appear to have effectively treated a genetic disorder by directly injecting a CRISPR therapy into patients' bloodstreams — overcoming one of the biggest hurdles to curing diseases with the gene editing technology.

The therapy appears to be astonishingly effective, editing nearly every cell in the liver to stop a disease-causing mutation.

The challenge: CRISPR gives us the ability to correct genetic mutations, and given that such mutations are responsible for more than 6,000 human diseases, the tech has the potential to dramatically improve human health.

One way to use CRISPR to treat diseases is to remove affected cells from a patient, edit out the mutation in the lab, and place the cells back in the body to replicate — that's how one team functionally cured people with the blood disorder sickle cell anemia, editing and then infusing bone marrow cells.

Bone marrow is a special case, though, and many mutations cause disease in organs that are harder to fix.

Another option is to insert the CRISPR system itself into the body so that it can make edits directly in the affected organs (that's only been attempted once, in an ongoing study in which people had a CRISPR therapy injected into their eyes to treat a rare vision disorder).

Injecting a CRISPR therapy right into the bloodstream has been a problem, though, because the therapy has to find the right cells to edit. An inherited mutation will be in the DNA of every cell of your body, but if it only causes disease in the liver, you don't want your therapy being used up in the pancreas or kidneys.

A new CRISPR therapy: Now, researchers from Intellia Therapeutics and Regeneron Pharmaceuticals have demonstrated for the first time that a CRISPR therapy delivered into the bloodstream can travel to desired tissues to make edits.

We can overcome one of the biggest challenges with applying CRISPR clinically.

—JENNIFER DOUDNA

"This is a major milestone for patients," Jennifer Doudna, co-developer of CRISPR, who wasn't involved in the trial, told NPR.

"While these are early data, they show us that we can overcome one of the biggest challenges with applying CRISPR clinically so far, which is being able to deliver it systemically and get it to the right place," she continued.

What they did: During a phase 1 clinical trial, Intellia researchers injected a CRISPR therapy dubbed NTLA-2001 into the bloodstreams of six people with a rare, potentially fatal genetic disorder called transthyretin amyloidosis.

The livers of people with transthyretin amyloidosis produce a destructive protein, and the CRISPR therapy was designed to target the gene that makes the protein and halt its production. After just one injection of NTLA-2001, the three patients given a higher dose saw their levels of the protein drop by 80% to 96%.

A better option: The CRISPR therapy produced only mild adverse effects and did lower the protein levels, but we don't know yet if the effect will be permanent. It'll also be a few months before we know if the therapy can alleviate the symptoms of transthyretin amyloidosis.

This is a wonderful day for the future of gene-editing as a medicine.

—FYODOR URNOV

If everything goes as hoped, though, NTLA-2001 could one day offer a better treatment option for transthyretin amyloidosis than a currently approved medication, patisiran, which only reduces toxic protein levels by 81% and must be injected regularly.

Looking ahead: Even more exciting than NTLA-2001's potential impact on transthyretin amyloidosis, though, is the knowledge that we may be able to use CRISPR injections to treat other genetic disorders that are difficult to target directly, such as heart or brain diseases.

"This is a wonderful day for the future of gene-editing as a medicine," Fyodor Urnov, a UC Berkeley professor of genetics, who wasn't involved in the trial, told NPR. "We as a species are watching this remarkable new show called: our gene-edited future."

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