Enlarge / It sure looks like a crab, but it isn't. Why are crab-like forms so common?
Many organisms on planet Earth aren't crabs. Dogs, for instancedefinitely not crabs. Science also suggests that humans are not, in fact, crabs. But a surprising number of creatures either are crabs or look a lot like them. For example, a hermit crab has a distinctly crab-like appearance but is not technically a real crab. Hermit crabs are not alone; over the history of life on Earth, there have been five separate cases in which decapod crustaceans have evolved this way, a process common enough that it has picked up a formal term: carcinization.
Around a year ago, this evolutionary process captured the imagination of the Internet. Headlines like Why everything eventually becomes a crab and Why Does Evolution Keep Turning Everything Into Crabs popped up. PBS even made a video.
"Everything" is clear hyperbolethe overwhelming majority of things on Earth are not crabs and seemingly have no plans to become them. But if there are benefits to having a crab-like shape on Earth, should we view that as a general rule of life? Could it hold true on other planets? If the process of carcinization operates here, it's not unreasonable to expect that it might happen elsewhere.
Because we take these things far too seriously, Ars spoke to experts on crabs, evolution, and alien life to find out. The answer: it's highly speculative, given that we haven't found lifecrab-like or otherwiseanywhere else, but it's not wholly impossible.
The reasons creatures evolved crabby features are still unknown, though there are numerous hypotheses. According to Jo Wolfe, a researcher at Harvard University's Department of Organismic and Evolutionary Biology, carcinization could be a mixture of genes and the environment. However, Wolfewho penned a paper on the topic last Marchalso noted that there are still no definitive answers.
There is no clear-cut reason why being a crab is better than not being a crab, she told Ars.
Yet crab-like forms are common enough that a number of the things we call crabs aren't all that closely related to crabs. For instance, a hermit crab is a decapod crustacean and part of a group called Anomura. Though they evolved to have crab-like features, they are not true crabs, which are in the infraorder Brachyura.
Wolfe said that the similar body plans may evolve because the body shape of a crab could have some advantages. Crab bodies tend to be compact and quite flat, with their abdomens folded up below. This could make them smaller targets for predators and could allow the crabs the ability to run and hide in smaller crevasses.
Claws might be a boon as well, Wolfe said. (Even though, again, having claws doesn't make a species a crablobsters have huge claws but aren't crabs.) But defending that argument is made harder by the fact that claws have multiple functions. Some crabs don't even use their claws for predation; a male fiddler crab, for instance, uses his one massive claw for sexual display.
Wolfe also suggested that there are probably genetic limits to carcinization. The genetic makeup of a species that evolved a crab-like body plan would need to have the right building blocks for the process. So, for example, both shrimp and crabs have a genetic toolkit that lets them produce many limbs and exoskeletons, while humans do notmeaning, most likely, there are no human-relative crabs on the horizon.
Right now, there's no evidence that there is any life, much less crab life, on other planets. Even if we found aliens that looked like crabs, they obviously wouldn't be crabs as we've defined them. With the right environment, however, crab-like aliens could hypothetically evolve elsewhere. Wolfe noted that any creatures on these theoretical planets would still need to have the right genetic building blocks to be capable of evolving into crab-like forms. Anda converse is also true: planets different from Earth are less likely to have crabs.
For example, a planet like Naboo in Star Warswhich has land, bodies of water, rock, etc.could be home to crabs, Wolfe said. On Earth, there are terrestrial crabs, which evolved from their marine kin. There are also terrestrial false crabs, such as the terrifying coconut crab. But largely, it seems that water or some kind of liquid on a planet would increase the odds of crabs being there.
If the form of a crab works because it makes it easier to scurry away into rocks and such, then some kind of rocky geography could also help a planet's chances of carcinization. Going back to the Star Wars analogy, planets like the desert world Tatooine or the gas giant Bespin (home of Cloud City) probably wouldn't have what it takes.
Crab-like creatures could also fill specific niches in planets with Earth-like environments, according to Arik Kershenbaum, a zoologist at the University of Cambridge and the author of 2020's The Zoologist's Guide to the Galaxy. Some crab species hang out at the bottom of the ocean and either eat the waste that flows down from higher in the water column or eat the other species that use the waste for nutrients.
Assuming another planet has aquatic life that dies and sinks to the bottom, that niche could also exist there. You could see the sort of evolutionary game playing out very similarly to what presumably happened on Earth, he told Ars.
This doesn't necessarily mean that the niche would be filled by crab-like critters, however. There are some benefits that crabs do have, like claws, multiple legs to scuttle around on, and segmented bodies, Kershenbaum said. But he said that our guesses about the purposes of evolutionary traits aren't always accurate. Further, he noted that in many cases, species simply inherit traits from previous generations, even after those traits no longer contribute to survival.
It seems likely that if there are space crabs, they'd probably come about on planets that have environments similar to Earth's. For her part, Wolfe doesn't necessarily expect that the emergence of life would need to be restricted to Earth-like planets. There could be all kinds of strange forms that evolve to live in alien environments. I think that you could [have crab-like creatures on other planets]. I also think you could get things that don't look like anything on Earth at all, she said.
Kershenbaum doesn't think that life in the stars needs to look exactly like life on Earth. Rather, weird and wacky alien life is just more likely to be rare by comparison. For example, there are plenty of rocky planets out there that probably have water on them, which could be a necessary precursor to life. But it's possible that life could exist in settings that are distinctly different from Earthlike spores living in the acidic atmosphere of Venus.
It seems likely that Earth-like planets are going to be relatively well-stocked with life compared to weird and wonderful planets, he said. More reasonable life is more likely to be common.
Charles Marshall, director of the University of California Museum of Paleontology, said, however, that it's a fairly narrow group of species that have evolved to become crabby on Earth. Moreover, these species are already pretty similar to crabs. You've already got to be so close to being a crab before you evolve into a crab, it's kind of a moot point, he told Ars. Life is produced in an enormous amount of morphologies, and crabbiness is just one of them.
The presence of crabby creatures on a planet could suggest the planet has the potential to develop into something interesting, Marshall added. He said that if he were to send a probe into space to look for life, he'd expect to see many worm-shaped thingsthey're quite common on Earth and have been around for more than 500 million years. For something to carcinize, there needs to be a vibrant ecology surrounding it. There would need to be predators for the organism to protect itself or hide from, plus a good variety of food. Worm-like forms probably don't need all of that.
Finding a crab might be indicative of a rich enough biosphere and a rich enough genomic potential that you may yet expect to evolve something like humans, he said. Therefore, searching for something like a crab might be a good idea. If [a planet hasn't] evolved something crab-like, you know you've found a world that's still relatively simple.
Go here to read the rest:
On Earth, things evolve into crabscould the same be true in space? - Ars Technica
- Days of our Lives' Suzanne Rogers on the Evolution of Maggie: "She Knows Who She Is Now, and She's Not Relying ... - Michael Fairman TV - March 14th, 2024 [March 14th, 2024]
- Kylie Jenner Talks About Her Style Evolution - The Cut - March 14th, 2024 [March 14th, 2024]
- Equator Coffees Unveils New Packaging Design, Reflecting Brand Evolution & Vision For The Future - Sprudge - March 14th, 2024 [March 14th, 2024]
- Rosewood Hotel Group Accelerates Growth And Evolution Across Its Four Distinctive Brands - Hospitality Net - March 14th, 2024 [March 14th, 2024]
- Thomson Reuters Unveils New Brand Evolution - Adweek - March 14th, 2024 [March 14th, 2024]
- Is It Becoming Acceptable to Speak of Design? - Discovery Institute - March 14th, 2024 [March 14th, 2024]
- Did Charles Darwin Convert to Christianity and Discredit Evolution on His Deathbed? - Snopes.com - March 14th, 2024 [March 14th, 2024]
- Milk, it's not just for mammals: An amphibian makes it too - NPR - March 14th, 2024 [March 14th, 2024]
- Discover Puerto Rico Debuts Evolution of Its Successful 'Live Boricua' Brand Campaign Aimed at Engaging Visitors ... - Yahoo Finance - March 14th, 2024 [March 14th, 2024]
- A Journey Through Time: The Evolution of Ras Al Khaimah Art - Business Wire - March 14th, 2024 [March 14th, 2024]
- Empowering Women: The Evolution and Innovation of coto Social Platform - CXOToday.com - March 14th, 2024 [March 14th, 2024]
- The Evolution of Da'Vine Joy Randolph - The Root - March 14th, 2024 [March 14th, 2024]
- Study on mating behaviors offers clues into the evolution of attraction - Phys.org - March 14th, 2024 [March 14th, 2024]
- Dragonball Evolutions live-action Goku says goodbye to Toriyama: Sorry we messed up - AS USA - March 14th, 2024 [March 14th, 2024]
- Investec, evolution of SMEs in the materials handling sector - Leasing Life - March 14th, 2024 [March 14th, 2024]
- Pride & Prejudice and the evolution of the female gaze on screen - Yahoo News UK - March 6th, 2024 [March 6th, 2024]
- Joe Wong's Musical Evolution - Shepherd Express - March 6th, 2024 [March 6th, 2024]
- A global survey of prokaryotic genomes reveals the eco-evolutionary pressures driving horizontal gene transfer - Nature.com - March 6th, 2024 [March 6th, 2024]
- Redefining Intelligence: Chimpanzees Break Through the Cultural Evolution Barrier - Medriva - March 6th, 2024 [March 6th, 2024]
- Mollusk Eyes Reveal How Future Evolution Depends on the Past - Quanta Magazine - March 6th, 2024 [March 6th, 2024]
- Levy Delves Into the Evolution of ADCs in NSCLC - OncLive - March 6th, 2024 [March 6th, 2024]
- The Snake Is The Spearhead of Reptile Evolution, But Why? - ScienceAlert - March 6th, 2024 [March 6th, 2024]
- 'A very special day: Birds linked to Darwins theory of evolution reintroduced to Galapagos Islands - Euronews - March 6th, 2024 [March 6th, 2024]
- Why the Powerhouses of Cells Evolve Differently in Plants - College of Natural Sciences - March 6th, 2024 [March 6th, 2024]
- Driving the DevOps Evolution: ArgoCD, Tekton and Seamless Migrations - DevOps.com - March 6th, 2024 [March 6th, 2024]
- Finding the Balance: The Evolution of Public Health Guidance Amidst Controversy - Medriva - March 6th, 2024 [March 6th, 2024]
- Insider Podcast: Paolini dishes on her Polish roots and hard-court evolution - WTA Tennis - March 6th, 2024 [March 6th, 2024]
- Interview: Sara Gruen and Rick Elice Talk About the Inspiration and Evolution of the New Musical Water for Elephants - TheaterMania.com - March 6th, 2024 [March 6th, 2024]
- The Evolution of the Laravel Welcome Page - Laravel News - March 6th, 2024 [March 6th, 2024]
- A Serpentine 'Explosion' 125 Million Years Ago Primed Snakes for Rapid, Diverse Evolution - Smithsonian Magazine - March 6th, 2024 [March 6th, 2024]
- The Evolution of Modern Technologies in Car Development - FinSMEs - March 6th, 2024 [March 6th, 2024]
- Milwaukee Transformed: From Bronzeville to Veterans Park, Aerial Timelapses Reveal City's Evolution - BNN Breaking - March 6th, 2024 [March 6th, 2024]
- The eyes are a gateway to evolution of daddy longlegs at least. - University of Wisconsin-Madison - March 6th, 2024 [March 6th, 2024]
- Adrian Newey: RB20 is the next step in Red Bull's design evolution - PlanetSport - March 6th, 2024 [March 6th, 2024]
- LiveScore releases its 'Evolution of Fan' report - Gambling Insider - March 6th, 2024 [March 6th, 2024]
- The loyalty program evolution makes its way to the full-service restaurant category - Nation's Restaurant News - March 6th, 2024 [March 6th, 2024]
- Teenage Mutant Ninja Turtles: The Last Ronin II - Re-Evolution #1 spoiler-free review: goes hard on the action, but ... - Gamesradar - March 6th, 2024 [March 6th, 2024]
- Exploring U.S. Financial Evolution: DAR Hosts Talk on Federal Reserve History in Thomasville - BNN Breaking - March 6th, 2024 [March 6th, 2024]
- Why cloud evolution needs a cohesive approach to succeed - CIO - March 6th, 2024 [March 6th, 2024]
- Gilead Sciences CEO on Company's Evolution and Commitment to the Bay Area - BioSpace - March 6th, 2024 [March 6th, 2024]
- Navigating the AI Quandary: Human Supremacy vs Machine Intelligence Evolution - BNN Breaking - March 6th, 2024 [March 6th, 2024]
- Denis Villeneuve breaks down the evolution of sandworms in 'Dune: Part Two' - Mashable - March 6th, 2024 [March 6th, 2024]
- Continued evolution of law improves governing capacity - Chinadaily.com.cn - China Daily - March 6th, 2024 [March 6th, 2024]
- The Evolution of the DEX Space with dYdX's CEO Antonio Juliano - Blockster - March 6th, 2024 [March 6th, 2024]
- Quick Commerce Evolution: 3PL Firms Aim for Same Day Delivery, Chasing Blinkit and Zepto's Lead - BNN Breaking - March 6th, 2024 [March 6th, 2024]
- What If...? Star Jeffrey Wright Addreses the Watcher's Evolution and 'Epic' Season 2 Finale - CBR - Comic Book Resources - December 31st, 2023 [December 31st, 2023]
- Evolution of the Connected Autonomous Vehicle - Ward's Auto - December 31st, 2023 [December 31st, 2023]
- A project to capture the evolution of human culture. - Psychology Today - December 31st, 2023 [December 31st, 2023]
- The Evolution of a Digital Soul. Beyond Code: A Journey of Heart and | by Mark Randall Havens | Dec, 2023 - Medium - December 31st, 2023 [December 31st, 2023]
- 4 Clues That Reid Is Finally Returning In Criminal Minds: Evolution Season 2 - Screen Rant - December 31st, 2023 [December 31st, 2023]
- Evolution of Samoyed and Kitten's Friendship Delights Internet: 'Wholesome' - Newsweek - December 31st, 2023 [December 31st, 2023]
- Crypto Evolution: Pullix (PLX) vs OKB (OKB) & KuCoin (KCS) - Crypto Reporter - December 31st, 2023 [December 31st, 2023]
- Alfa Romeos mediocre F1 season heralded its era of evolution: Prime Tire - The Athletic - December 31st, 2023 [December 31st, 2023]
- Beyond The Uniform: 10 Years of Evolution in SYNC Performance's Custom Program - SkiRacing.com - December 31st, 2023 [December 31st, 2023]
- Why SZA's evolution into a popstar has earned her recognition as artist of the year - Salon - December 31st, 2023 [December 31st, 2023]
- AI in 2023 Rises, Falls and Evolution - Finance Magnates - December 31st, 2023 [December 31st, 2023]
- Indonesia's Indosat pursues evolution from telecom to tech company - Nikkei Asia - December 31st, 2023 [December 31st, 2023]
- EdTech Evolution: 3 Stocks Educating the Next Generation - InvestorPlace - December 31st, 2023 [December 31st, 2023]
- Informa Tech Interview with Huawei about voice evolution and innovations at 5G Core Summit 2023 - Informa Tech ... - Light Reading - December 31st, 2023 [December 31st, 2023]
- Looking ahead: What will the DeFi evolution look like in 2024? - Ledger Insights - Ledger Insights - December 31st, 2023 [December 31st, 2023]
- Why Cat Bohannon wrote 'Eve, How the Female Body Drove 200 Million Years of Human Evolution' | India News ... - IndiaTimes - December 31st, 2023 [December 31st, 2023]
- The smart-design evolution of the laboratory space - pharmaphorum - December 31st, 2023 [December 31st, 2023]
- The WILD Evolution of Teenage Mutant Ninja Turtles TMNT (VIDEO) - FandomWire - December 31st, 2023 [December 31st, 2023]
- The supernatural invades American museums via indigenous artifacts - Why Evolution Is True - December 31st, 2023 [December 31st, 2023]
- Baleen Whales First Evolved Large Body Size in Cold Southern Waters, New Fossil Shows - Sci.News - December 31st, 2023 [December 31st, 2023]
- The Evolution of Identity in Taiwan The Diplomat - The Diplomat - December 31st, 2023 [December 31st, 2023]
- From the Archive: The Evolution Of Hockey Pools - The Hockey News - December 31st, 2023 [December 31st, 2023]
- 'X-Men: Evolution' Is Better Than 'X-Men: The Animated Series' - Collider - December 31st, 2023 [December 31st, 2023]
- Unveiling the Silver Screen: The Evolution of Celebrity Nudity in Cinema - The Hype Magazine - December 31st, 2023 [December 31st, 2023]
- Are Humans Still Evolving? 'Maybe More Rapidly Than Ever,' Says Scientist - Newsweek - December 31st, 2023 [December 31st, 2023]
- The Intersection of Real Estate and Fintech: Evolution, Impact of Policies, and Global Dynamics - CXOToday.com - December 31st, 2023 [December 31st, 2023]
- Kyle Richards' Style Evolution: Her Best Looks - Us Weekly - December 31st, 2023 [December 31st, 2023]
- Criminal Minds: Evolution Season 2's "Deeper Secrets" Teased By Aisha Tyler - Screen Rant - December 31st, 2023 [December 31st, 2023]
- Saturday: Hili dialogue Why Evolution Is True - Why Evolution Is True - December 31st, 2023 [December 31st, 2023]
- NBA 2K24 MyTEAM New Year Resolution Adds 14 Evolution Cards - ClutchPoints - December 31st, 2023 [December 31st, 2023]
- dive into the history of NASA's logo evolution from the space ... - Designboom - November 8th, 2023 [November 8th, 2023]
- Resolving the puzzle of same-sex sexual interactions - Nature.com - November 8th, 2023 [November 8th, 2023]
- The History and Evolution of Black Friday And How It Got Its Name - Yahoo Life - November 8th, 2023 [November 8th, 2023]
- Evolution of Terran R, with Tim Ellis (Relativity Space) - Payload - November 8th, 2023 [November 8th, 2023]
- Brownell Raves About Breakout Junior's Evolution - The Clemson Insider - November 8th, 2023 [November 8th, 2023]