The prevailing theory that mammals only flourished after an asteroid strike wiped out the dinosaurs 66 million years ago is doubly wrong, according to a study published Wednesday.
Our warm-blooded predecessors thrived and spread over millions of years even as Tyrannosaurus and other flesh-ripping monsters lorded over the planet, researchers reported.
Moreover, these mammals took a big hit when the asteroid slammed into Earth, creating a hemispheric firestorm followed by a prolonged, bone-chilling drop in global temperatures.
"The traditional view is that mammals were suppressed during the 'age of dinosaurs'," and thus held in check, said co-author Elis Newham, a doctoral student in evolutionary biology at the University of Chicago.
"However, our findings were that therian mammals -- the ancestors of most modern mammals -- were already diversifying considerably before the Cretaceous-Tertiary extinction event," also known as the K-Pg boundary.
The researchers pulled together dozens of studies that challenged and chipped away at the old theory.
But key to the new conclusion, they said, was teeth.
An analysis of hundreds of molars from mammals alive during the 20 million years before the K-Pg boundary revealed a huge variety of shapes -- a telltale sign of varied diets and species diversity.
Surviving an extinction event
The scientists were surprised to find a sharp decline in the number of mammals after the asteroid crash.
"I didn't expect to see any sort of drop," said lead author David Grossnickle, also of the University of Chicago.
"It didn't match the traditional view that after the extinction, mammals hit the ground running."
Once again, teeth told a story, this time revealing which mammals made it across the K-Pg boundary, and which did not.
Those with molars indicating a specialised diet -- only bugs or only plants, for example -- were less likely to weather the disaster than those with all-purpose chompers ready to eat whatever was available.
The findings, published in Proceedings of the Royal Society B, may hold a lesson for today's world, Grossnickle said.
Scientists say Earth is experiencing another mass extinction event, driven mainly by climate change -- only the sixth in the last half billion years, he pointed out.
"The types of survivors that made it 66 million years ago, mostly generalists, might be indicative of what will survive in the next hundred years, or the next thousand," Grossnickle said in a statement.
The Cretaceous-Tertiary extinction wiped out three-quarters of the plant and animal species on Earth, including all dinosaurs which could not fly.
With the exception of a few crocodiles and sea turtles, there is no evidence that tetrapods -- four-limbed vertebrates -- weighing more than 25 kilos (55 pounds) survived.
The discovery in the 1990s of the 180-kilometre (110-mile) wide Chicxulub crater straddling the Yucatan Peninsula and the Gulf of Mexico, pinpointed the likely spot where the asteroid hit.
After the K-Pg event, new forms of mammals such as horses, whales, bats, and primates emerged and spread in a dinosaur-free world.
AFP
Wed Jun 08 2016
This file photo taken on December 16, 2015 shows an original and nearly complete skeleton of a Tyrannosaurus Rex dinosaur named " Tristan Otto " on display at Berlin's Natural History Museum. - AFP Photo/John MacDougall
Who is Prabowo Subianto, incoming president of Indonesia?
A wealthy ex-general with ties to Indonesia's popular outgoing president and its dictatorial past, looks set to be its next leader.
Iran's supreme leader says Hamas leader's death will not halt 'Axis of Resistance'
The "Axis of Resistance", built up with years of Iranian support, includes Hamas, the Lebanese Hezbollah group, the Houthi movement in Yemen, and various Shi'ite groups in Iraq and Syria.
Putin says Russia willing to seek compromises between Iran and Israel
Russia is ready to help seek compromises between arch-foes Israel and Iran, President Vladimir Putin said on Friday, saying these would be difficult but possible.
What proposals will Russia push at the BRICS summit?
The proposal is also to establish a BRICS reinsurance company to allow uninterrupted shipment of goods and key commodities between members.
Indonesia's free meals plan in the spotlight as Prabowo readies for office
Prabowo calls the programme one of the main drivers of economic growth, eventually set to add an estimated 2.5 million jobs.
Astro AWANI's revamped English news website, AWANI International, launches on Oct 21
Astro AWANI's revamped English platform delivers in-depth global news and expert analysis to keep you informed on key developments.
Israeli strikes kill 33 people in Jabalia refugee camp in Gaza, medics say
Residents of Jabalia said Israeli tanks had reached the heart of the camp after pushing through suburbs and residential districts.
Liam Payne's ex-partner calls for media restraint after 'painful' death
Cheryl Tweedy used her statement to urge the media to remember they had a seven-year-old son, Bear, who could read the reports.
Analysts: Indonesia's strong MoF leadership team to boost investor confidence
Sri Mulyani Indrawati as head of Indonesia's Ministry of Finance is expected to instil confidence among investors.
Biden offers both a carrot and a stick to Israel as his term nears an end
Israel has frequently resisted US advice and has caused political difficulties for the Biden administration.
Putin says BRICS will generate most of global economic growth
Russian President Vladimir Putin will host a summit of the group in the city of Kazan on Oct. 22-24.
ISIS Malaysia's perspective of Budget 2025
An excellent rakyat-centric budget under the overarching principle of a caring and humane economy.
Budget 2025: Record increase in STR, SARA aid initiatives
The government will provide a significant boost to the Sumbangan Tunai Rahmah (STR) and Sumbangan Asas Rahmah (SARA) initiatives next year.
Budget 2025: EPF contributions to be made mandatory for foreign workers – PM Anwar
The government plans to make it compulsory for all non-citizen workers to contribute to the Employees Provident Fund (EPF).
What policies to expect from Indonesia's new President Prabowo
Prabowo will be open to foreign investment, his aide has said, such as by offering investors management of airports and sea ports.
Budget 2025: Govt allocates RM470 mil to empower women's participation in PMKS
The Women's Leadership Apprenticeship Program will be intensified as an effort to produce more female corporate personalities.
Israel sends more troops into north Gaza, deepens raid
Residents of Jabalia in northern Gaza said Israeli tanks had reached the heart of the camp, using heavy air and ground fire.
Indonesia ramps up security ahead of Prabowo's inauguration
Prabowo Subianto will be sworn in as Indonesia's president on Sunday with Vice President-elect, Gibran Rakabuming Raka, also taking office.
Immediate allocation of RM150 mil for local authorities, DID to tackle flash floods
Datuk Seri Anwar Ibrahim said this allocation is intended to address the recent flash floods that hit the capital and several major towns.
Budget 2025: Sabah, Sarawak to continue receiving among highest allocations - PM
Sabah and Sarawak continues to be prioritised under Budget 2025, with allocations of RM6.7 billion and RM5.9 billion respectively.