Research reveals a new evolutionary feature that separates humans from other primates.
- Researchers find a new feature of human evolution.
- Humans have evolved to use less water per day than other primates.
- The nose is one of the factors that allows humans to be water efficient.
A model of water turnover for humans and chimpanzees who have similar fat free mass and body water pools.
Credit: Current Biology
One million year old mammoth DNA more than doubles the previous record and suggests that even older genomes could be found.
- Scientists extracting DNA from mammoth teeth have set a new record for the oldest DNA ever sequenced.
- The new record holder may also be a member of a new species of mammoth, but that remains to be proven.
- The findings suggest that DNA as old as 2.6 million years old could be decoded.
Mammoth Molars<p> The DNA was taken from three sets of mammoth teeth discovered in Siberia in the 1970s. The three samples, named Krestovka, Adycha, and Chukochya, are too old for carbon dating techniques to be useful. Their ages were instead determined using methods such as <a href="https://en.wikipedia.org/wiki/Radiometric_dating" target="_blank" rel="noopener noreferrer">radiometric dating.</a> </p><p>Krestovka is the oldest of the three, dating back to about 1.1 or 1.2 million years ago. In addition to setting the record for the oldest animal to have DNA sequenced from it, Krestovka appears to be the first known example from a new lineage of mammoth. It seems to belong to another branch of the evolutionary tree that left no living decedents. However, some of its DNA also exists in the Colombian mammoth's genetics, which raises other questions.</p><p>While it is too soon to say that Krestovka is from a new mammoth species, the possibility is there. If it is, then it also suggests that the Columbia mammoth could be a hybrid species between this unknown branch and the woolly <a href="https://gizmodo.com/million-year-old-mammoth-teeth-contain-oldest-dna-ever-1846287115" target="_blank" rel="noopener noreferrer">mammoth</a>. This would be particularly exciting, as evidence for hybridization creating new species is rare.</p><p>Adycha dated back about one million years. It is thought to be a steppe mammoth, a larger, less hairy ancestor of the woolly mammoth. Steppe mammoths lived across Eurasia but were considered to be best suited for warmer climates than Siberia. Some of the DNA fragments also imply that adaptations for surviving in cooler temperatures, revealed in genes related to fat deposits, thermal regulation, and the circadian rhythm, appeared earlier in the evolutionary tree than previously thought. </p><p>Chukochya is the youngest of the three. Dated to some point between 500,000 and 800,000 years ago, it was an early example of a woolly mammoth. </p>
Why is this exciting, exactly?<iframe width="730" height="430" src="https://www.youtube.com/embed/gHbYJfwFgOU" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe><p> DNA breaks down fairly quickly in most environments. Exposure to bacteria, water, ultraviolet light, or enzymes breaks it down. Even in the permafrost, where conditions are more favorable, these factors slowly whittle away at the information until little is left. That makes this find so exciting — it is remarkable that this much information endured a million years in the <a href="https://www.nytimes.com/2021/02/17/science/DNA-mammoth.html" target="_blank" rel="noopener noreferrer">ground</a>. </p><p>The previous record-holder was the DNA of a 750,000-year-old horse found in the permafrost of the <a href="https://www.sciencemag.org/news/2013/06/700000-year-old-horse-becomes-oldest-creature-sequenced-genome" target="_blank" rel="noopener noreferrer">Yukon</a>. In principle, it is possible to find DNA as old as the oldest permafrost: 2.6 million years old. Protein sequences last longer; the current <a href="https://elifesciences.org/articles/17092" target="_blank" rel="noopener noreferrer">record holder</a> is dated back to 3.8 million years but reveal much less information.</p><p>While the DNA from these mammoth teeth was quite fragmented, modern technology made putting the pieces together possible. By comparing what remained with the DNA of elephants and younger mammoth samples, the scientists could isolate the fragments that were unique to the specimen.</p><p>Ludovic Orlando, the head of the team which held the previous record, expressed his <a href="https://www.sciencemag.org/news/2021/02/mammoth-molars-yield-oldest-dna-ever-sequenced" target="_blank" rel="noopener noreferrer">excitement</a> at losing it, "I love this paper. I have been waiting since 2013 [for] our world record for the oldest genome to be broken."</p>
So do these findings mean we’re getting mammoth clones?<iframe width="730" height="430" src="https://www.youtube.com/embed/8c-EWSmOgDc" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe><p> Not yet. As mentioned, these sequences are incomplete and damaged due to their age. The cloning of mammoths using more complete samples of their DNA is generally thought to be a bit <a href="https://www.washingtonpost.com/national/health-science/can-scientists-bring-mammoths-back-to-life-by-cloning/2015/02/06/2a825c8c-80ae-11e4-81fd-8c4814dfa9d7_story.html" target="_blank" rel="noopener noreferrer">unfeasible</a>. Even if it could be done, there is a question of what you'd do with the animal you've created. While some have suggested bringing the mammoths back and putting them in <a href="https://science.sciencemag.org/content/308/5723/796.1" target="_blank" rel="noopener noreferrer">Siberia</a>, the benefits of doing this remain unstated. </p><p>However, the findings shine a light on evolutionary paths previously unknown to us and prove that these methods can work on other samples, potentially including even older ones. </p><p> So, even if you're not going to see a cloned mammoth any time soon, you may see a better model of one at the natural history museum and a better picture of how life on Earth, including our species, changes over time in response to shifting environmental factors. It's a great takeaway from studying some old teeth.</p>
A study of europium crystals shows the planet was mostly flat during its middle ages.
Credit: Alchemist-hp, CC0 public domain
The island rule hypothesizes that species shrink or supersize to fill insular niches not available to them on the mainland.
- Brookesia nana, the nano-chameleon, may be the smallest vertebrate ever discovered.
- The "island rule" states that when new species migrate to islands, they may shrink or grow as they evolve to fill new ecological niches.
- It remains unclear whether the island rule can explain the nano-chameleon or nature's other extreme miniaturizations.
Bigger isn't always better<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTYzNTY0OS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNjM5MzYwMH0.ge-xLd6L6EXkTSUSDmAWCdoLsTsWmK0-54LILO_4pt8/img.jpg?width=1245&coordinates=0%2C279%2C0%2C280&height=700" id="1db5a" class="rm-shortcode" data-rm-shortcode-id="62958849d69721c1050aee9b45006650" data-rm-shortcode-name="rebelmouse-image" data-width="1245" data-height="700" />
The New Zealand little spotted kiwi evolved to be small to fill an ecological niche. Before the arrival of humans, its island ecosystem contained no land mammals to prey on these flightless birds.
Credit: Wikimedia Commons<p>Because of their geographic isolation, islands can have powerful effects on the evolution of their residential species. The massive Komodo dragon prowls its namesake island. The <a href="https://www.wired.com/2015/01/absurd-creature-of-the-week-barbados-threadsnake/" target="_blank" rel="noopener noreferrer">Barbados threadsnake</a> is thin enough to slither through a straw. And the fossil record recounts a history of unusually sized and bedecked creatures who established homes far from the mainland, such as <a href="https://prehistoric-fauna.com/Hoplitomeryx-matthei" target="_blank" rel="noopener noreferrer">the <em>Hoplitomeryx</em> of the Mikrotia fauna</a>.</p><p>One hypothesis for evolution's insular experimentation is "the island rule." The rule states that after establishing themselves on an island, smaller species will tend to evolve into oversized versions of their mainland ancestors. Meanwhile, larger species will tend to evolve into smaller variations. These processes are known as insular gigantism and insular dwarfism, respectively. They do this to fill the ecological niches available to them, which often differ from those they filled on the mainland.</p><p>The rule was first formulated by evolutionary biologist Leigh Van Valen and based on a <a href="https://www.nature.com/articles/202234a0" target="_blank" rel="noopener noreferrer">1964 study</a> by mammologist J. Bristol Foster—which is why it is also known as Foster's rule. Since then, many observational studies have corroborated the island rule, and there is <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0040334" target="_blank" rel="noopener noreferrer">even evidence</a> to suggest that new species introduced to islands will, for a time, evolve more rapidly to fill available niches.</p><p>A flock of migrant birds, for example, may find an island's lack of mammalian and reptilian predators opens the ground-living niche once forbidden to them. Such birds would then be free to grow larger, forage below the canopies, and lose the ability of flight.</p><p>This appears to be the origin story for New Zealand's flightless birds including <a href="http://nzbirdsonline.org.nz/species/south-island-giant-moa" target="_blank" rel="noopener noreferrer">the giant moa</a>, which, at six-feet tall, is the tallest bird on record. This megafauna enjoyed all the benefits of being large and in charge: fewer predators, wider ranges, access to more and varied foods, and the ability to better survive trying times. The species enjoyed island life until roughly 600 years ago, when humans arrived on the scene and <a href="https://www.sciencemag.org/news/2014/03/why-did-new-zealands-moas-go-extinct" target="_blank" rel="noopener noreferrer">hunted them to extinction</a>.</p><p>Conversely, large species may find island living restrictive as there's less room or food when compared to their mainland nurseries. Because of this, evolution may select for smaller body sizes as such bodies require less energy, and therefore fewer resources, to survive and reproduce. </p><p>This is the theory behind the miniaturization of the <a href="https://www.nps.gov/chis/learn/historyculture/pygmymammoth.htm" target="_blank" rel="noopener noreferrer">Channel Islands pygmy mammoths</a>. As the story goes, in the search for food, a herd of Columbian mammoths embarked on a journey to the super island Santaroasae. Over time, the island was cut off from the mainland. Food became scarce, and smaller mammoths had an easier time surviving and reproducing, thus passing on their Shrinky-Dink genes. Thanks to a lack of oversized predators, such evolution proved fruitful, and in less than 20,000 years, the giant Columbian mammoths evolved into a new species—the (relatively) pint-sized, 6.5-foot-tall pygmy mammoths.</p><p>To be clear, the island rule doesn't state that any species that washes ashore must go either Lilliputian or Brobdingnag. It only states that if an ecological niche becomes available and improves survival and reproductive success, then such a change is likely.</p>
Thanks to that island living?<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="c01cabce7b0b2b48a3734896c4a396db"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/SK7oHmJdDOM?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>Such constrained growth may be the cause of the Jaragua dwarf gecko's bantam evolution. The <a href="https://science.psu.edu/news/worlds-smallest-lizard-discovered-caribbean" target="_blank" rel="noopener noreferrer">gecko eats tiny insects</a> and may be filling a niche that's unavailable on the North American continent with its many, many insectivores. In fact, the island rule may explain why islands are so rich with endemic species—particularly the Caribbean, which is considered <a href="https://www.oecs.org/perb_docs/bc_part2_intro_hotspot.pdf" target="_blank" rel="noopener noreferrer">a biodiversity hotspot</a>.</p><p>Of course, scientific rules are only provisional, and scientists are prepared to revise or completely disregard a hypothesis should new evidence appear. In a field as new as biogeography, the question of whether the island rule is truly a "rule" remains an open and hotly debated question. </p><p><a href="https://onlinelibrary.wiley.com/doi/full/10.1111/jbi.13160" target="_blank" rel="noopener noreferrer">One systematic review</a> found empirical support for the island rule to be low, while <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2007.1056" target="_blank" rel="noopener noreferrer">another analysis</a> argued the rule is simply a recognition of "a few clade-specific patterns." The latter's authors conclude that "[i]nstead of a rule, size evolution on islands is likely to be governed by the biotic and abiotic characteristics of different islands, the biology of the species in question and contingency."</p><p>That brings us back to the newly discovered nano-chameleon. While it seems to follow the island rule—Madagascar being an island known for its rich biodiversity—there is a wrinkle. The species' closest relative lives right next door. <em>Brookesia karchei</em> is near twice the size of the nano-chameleon but ranges in the same mountains on mainland Madagascar. </p><p>If the nano-chameleon evolved to fill an ecological niche, why didn't those same environmental pressures miniaturize the karchei chameleon? If not the island rule, what did lead to the nano-chameleon's smaller size? As is often the case in science, further evidence may one day answer these questions.</p>
For the first time, it was discovered that nonphotosynthetic bacteria have a circadian clock.
- For the first time, nonphotosynthetic bacteria are shown to have a circadian clock.
- B. subtilis thrives in the gastrointestinal tracts of humans as well as grass-feeding ruminants.
- The researchers believe that this rhythm provides bacteria with an advantage.