{"id":490483,"date":"2026-06-13T06:12:22","date_gmt":"2026-06-13T06:12:22","guid":{"rendered":"https:\/\/www.newsbeep.com\/il\/490483\/"},"modified":"2026-06-13T06:12:22","modified_gmt":"2026-06-13T06:12:22","slug":"a-lack-of-sex-held-back-lifes-diversity-for-millions-of-years","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/il\/490483\/","title":{"rendered":"A lack of sex held back life\u2019s diversity for millions of years"},"content":{"rendered":"

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image:\u00a0<\/p>\n

Artist’s impression of a Edicaran animal community.<\/p>\n

view more\u00a0<\/a><\/p>\n

Credit: Hugo Salais<\/p>\n

The way that Earth\u2019s first animals reproduced held back life\u2019s diversity for millions of years, until stress and competition led to the development of sexual reproduction, which in turn accelerated the pace of evolution.<\/p>\n

Researchers from the University of Cambridge studied fossils from the oldest-known animals on Earth, dating from 574 million years ago, and found that asexual reproduction slowed the pace of evolution to a crawl, since it limited competition between different groups.<\/p>\n

Their results, reported in the journal Nature Ecology and Evolution<\/a>, could help explain a longstanding puzzle in palaeontology: why animal life appeared on Earth but then barely changed for millions of years, before a second wave of diversification gave evolutionary progress a major boost.<\/p>\n

After billions of years of microbial life, during the Ediacaran period, between 635 and 539 million years ago, life exploded in size and the first animals appeared. Some of these earliest animals, such as Fractofusus, could grow as tall as two metres, although most were much smaller.<\/p>\n

These animals looked more like ferns than any animal we would recognise today: they do not appear to have mouths, organs or means of movement, so they are thought to have absorbed nutrients from the water around them. And like most Ediacaran life forms, they disappeared from the fossil record at the beginning of the Cambrian period 540 million years ago, making it difficult for scientists to link them to any modern life forms.<\/p>\n

Researchers have previously determined that these early animals reproduced asexually, by sending out clones via stolons or runners, like modern strawberry plants. In the rich waters of the Ediacaran, they thrived.<\/p>\n

\u201cLife was pretty nice during the Ediacaran, so the need for sex was rather limited,\u201d said lead author Dr Emily Mitchell from Cambridge\u2019s Department of Zoology. \u201cThere was relatively little competition, so there was no real pressure to change anything.\u201d<\/p>\n

Mitchell and her co-author Professor Andrea Manica used a combination of laser scanning, spatial analysis and artificial intelligence to study fossils from Mistaken Point in Newfoundland, one of the world\u2019s richest sources of fossils from the Ediacaran, to help determine why early animal evolution slowed down, and why it might have sped up again.<\/p>\n

The researchers first showed that asexual, stolon-based reproduction limited competition, then built a computer model to simulate how early animal communities might behave under different reproductive strategies. They ran the model thousands of times while a simple neural network helped narrow down which simulations best matched the diversity patterns seen in the fossil record. This approach, known as Approximate Bayesian Computation, allowed the researchers to work backwards from the real data to estimate how far organisms spread and how strongly they competed for resources.<\/p>\n

Using this method, the researchers showed that limited dispersal linked to asexual, runner-based reproduction could explain why early animal communities had relatively few species, and why a later shift toward wider dispersal and sexual reproduction coincided with a sudden burst of evolutionary diversity.<\/p>\n

Competition and stress have been prime drivers of evolution for billions of years, but in the deep waters of the Ediacaran, asexual reproduction meant that competition was limited. \u201cIf you\u2019re connected to your neighbour by these runners, then you\u2019re sharing nutrients and you don\u2019t need to compete with them,\u201d said Manica.<\/p>\n

However, as life in the Ediacaran slowly spread from the deep ocean to shallower waters, early animals faced more pressures: tides, storms, changing temperatures and nutrient levels all would have made life more precarious, leading to increased competition for resources.<\/p>\n

\u201cIf you\u2019re suddenly in an environment where you\u2019re essentially getting killed a couple of times per year, then that changes everything,\u201d said Mitchell. \u201cStress essentially leads to sexual reproduction, and when that happens, we can see a massive increase in dispersal distances as animals attempt to colonise new areas due to an increase in competition.\u201d<\/p>\n

As these early animals adapted to both a new mode of reproduction and new habitats, there was a corresponding increase in diversification, leading to the Ediacaran \u2018second wave\u2019 of animal evolution, a process that accelerated further in the Cambrian, once animals became mobile.<\/p>\n

The research was supported by the Natural Environment Research Council (NERC), part of UK Research and Innovation (UKRI). Emily Mitchell is a Fellow of Newnham College, Cambridge. Andrea Manica is a Fellow of Clare College, Cambridge.<\/p>\n

Journal<\/p>\n

Nature Ecology & Evolution<\/p>\n

Article Title<\/p>\n

The influence of reproductive mode on resource competition and diversity patterns in Ediacaran early animal communities<\/p>\n

Article Publication Date<\/p>\n

9-Jun-2026<\/p>\n

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.<\/p>\n","protected":false},"excerpt":{"rendered":"image:\u00a0 Artist’s impression of a Edicaran animal community. view more\u00a0 Credit: Hugo Salais The way that Earth\u2019s first…\n","protected":false},"author":2,"featured_media":490484,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22],"tags":[242,85,46,141],"class_list":["post-490483","post","type-post","status-publish","format-standard","has-post-thumbnail","category-environment","tag-environment","tag-il","tag-israel","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/490483","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/comments?post=490483"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/490483\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media\/490484"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media?parent=490483"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/categories?post=490483"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/tags?post=490483"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}