Did stress destroy the dinosaur?
HOW 70 MILLION-YEAR-OLD EGGS COULD EXPLAIN A MYSTERIOUS DISAPPEARING ACT
Sunday 28 February 1999
Analysis of 70 million-year-old dinosaur egg shells now suggests prehistoric creatures could, in fact, have done with hugs of reassurance and that they were just as stressed out as any modern-day commuter.
The research is based on the fact that some dinosaur eggs are "double- shelled", a recognised sign of stress in the eggs of modern animals, such as turtles, crocodiles and chickens. Scientists are now speculating that stress was a factor in the death of the dinosaurs - or that it was symptomatic of the apocalyptic event which wiped them out 65 million years ago.
Scientists in Glasgow and Montana in the US have carried out research showing that the eggs of a small dinosaur called Troodon formosus, which lived around 76 million years ago, displayed similar signs of stress to those exhibited by turtles which have been subjected to human interference and pollution.
"The phenomenon of double egg shells is not restricted to modern-day birds. It also existed in dinosaurs," says Professor Sally Solomon, of the poultry research unit of Glasgow University's Veterinary School, which carried out the research.
The findings have been backed by Dr Angela Milner, head of fossils and vertebrates at the Natural History Museum in London. "It's fair to say that if you see abnormalities in the eggs of modern birds like chickens you can expect the abnormalities to arise for the same reasons in dinosaurs," she says.
Scientists liken egg shells to fingerprints because of the detail they can provide about the environment in which they were laid. They have learned that chickens and turtles delay laying their eggs in times of danger, allowing an extra layer of calcium - or a double shell - to be formed.
"We know dinosaurs held on to their eggs for longer than they should have. So we can wonder at what the environmental factors were that caused them to do that," says Prof Solomon. "And what contribution that fact made to the end of a species."
Double-shelled eggs are widely known to be formed by turtles as a result of stress and pollution, says Prof Solomon. "Marine turtles come ashore during the hours of darkness to lay their eggs but in some parts of the world this magnificent act of mother nature has become something of a tourist attraction.
"Turtles are not used to an audience. I've seen many occasions when the mother has simply returned to the water and not laid her egg." Pollution has also been found in Mediterranean turtles that retain their eggs, suggesting mothers sense the conditions are not right to lay them.
Double-shell eggs have also been seen in chickens, though surprisingly they are common among free range poultry, which are more likely to encounter foxes and barking dogs, than battery farm hens, whose monotonous routine is less likely to produce the factors which would cause them to retain their eggs.
"These creatures seem to be saying `I'm not going to lay my egg because it is vulnerable,' and they decide to hold on to it for a while," says Prof Solomon.
A number of environmental factors could have been stressful to dinosaurs, including climate change, crashing meteor- ites and rising sea levels, according to Dr Milner. All such events could cause stress in any dinosaur, regardless of size or its place in the food chain, she said.
"These eggs were laid well before the Earth was hit by a meteorite, so they provide interest to those who believe dinosaurs died out because of longer- term reasons, such as climate change," says Dr Milner. "We know that at the time the Troodon lived major changes in sea levels were taking place."
If dinosaurs were regularly laying double-shelled eggs they could have contributed to their own demise. "Holding on to the eggs is actually a retrograde step," says Prof Solomon, one that makes it harder for offspring to survive. "If laying is delayed it can lead to the formation of a heavily calcified egg shell, which is too much for the hatchling to break through and affects the amount of oxygen the embryo can get."
- 1 Migrant crisis: Greek soldier saved 20 people singlehandedly off Rhodes beach
- 2 The confessions of men who ordered mail-order brides
- 3 UK weather: Britain braced for snow as arctic air mass moves in
- 5 'Isis' schoolgirls: Missing British teenager tweets picture of her Syrian takeaway
Migrant crisis: Greek soldier saved 20 people singlehandedly off Rhodes beach
Aaron and Melissa Klein: Oregon anti-gay bakers ordered to pay $135,000 after refusing to make cake for same-sex wedding
UK weather: Britain braced for snow as arctic air mass moves in
Power of Nepal earthquake was equivalent to 20 huge atomic bombs
Nepal earthquake video: Terrifying footage shows moment avalanche hit Everest Base Camp
General Election 2015: Chuka Umunna on the benefits of immigration, humility – and his leader Ed Miliband
The sickening truth about food banks that the Tories don't want you to know
Migrant boat disaster: Ukip candidate mocks victims in sickening Twitter post
Nigel Farage wants the BBC to stop making programmes like Doctor Who, Strictly Come Dancing, and Top Gear
Global warming: Scientists say temperatures could rise by 6C by 2100 and call for action ahead of UN meeting in Paris
General Election 2015: Britain would become a 'communist dictatorship' under Ed Miliband and Nicola Sturgeon, claims wife of Michael Gove
£16000 - £25000 per annum: Recruitment Genius: A Photographer/ Floor planner /...
£30000 - £40000 per annum: Ashdown Group: Front-End Developer - Guildford/Craw...
£13500 - £15000 per annum: Recruitment Genius: A Customer Service Assistant is...
£16000 - £35000 per annum: Recruitment Genius: An ambitious and motivated Sale...