The extinction of the dinosaurs was most probably caused by an asteroid hitting the Earth - but what would have happened if the giant space rock had missed?

For a long time it was thought that dinosaurs were a lumbering, cold-blooded extinction just waiting to happen. Even the word dinosaur has come to mean something that has outlived its time. The scientific argument was that as cold-blooded creatures, dinosaurs would not have stood a chance of surviving an ice age.

"According to the first imaginings of palaeontologists and the general public about dinosaurs, we thought of them as reptiles," says Kristi Curry-Rogers, from the Science Museum of Minnesota. 'Reptile' is a word which comes with a lot of other connotations, like cold-blooded, slow-moving, sprawling, scaly skins, kind of stupid."

But more recent discoveries, such as dinosaur fossils in both polar regions, reveal that these animals were far more adaptable than previously thought.  Dr Curry-Rogers has analysed fossilised bones from Late Cretaceous (65-99 million years ago) dinosaurs and found them to have more in common with mammals and birds than reptiles.

"They were perfectly well-adapted to deal with the problems of maintaining a body temperature," Dr Curry-Rogers told the BBC's Horizon programme.

In other words, some of the dinosaurs were more than equipped to survive almost anything that the evolving planet had to throw at them.

Ongoing domination

"They were the superlatives; they were the biggest, the heaviest, the meanest, the longest. You name it, dinosaurs were it," says fellow palaeontologist Phil Currie, from the University of Alberta in Canada, who has access to one of the richest areas of dinosaur research in the world.

"The badlands of Alberta clearly show that at the end of the Cretaceous, dinosaurs were extremely successful still," says Professor Currie, who points to dozens of different dinosaur species living in that one environment at the same time.Had the asteroid missed, he believes, dinosaurs would have continued to dominate.

"We wouldn't have the modern animals that we're used to. Giraffes and elephants and so on; they just wouldn't have evolved because dinosaurs would still be here," says Professor Currie.

Instead of elephants, there would be large plant-devouring sauropods. In place of lions on the plains of Africa would be tyrannosaurs. Adaptable dinosaurs had it all covered. Dinosaurs could have comfortably colonised many environments, from polar conditions to regions of rivers and forests, jungle and deserts.
 A world with dinosaurs in it would be at the expense of most, if not all, of the mammals that we are familiar with today - and all that we rely on them for. No cows, no sheep, no cats equal no milk, no leather, no wool, no domestic companionship. But milk aside, there could be perfectly suitable dino-substitutes of all kind. A Protoceratops could be as farmable as a pig with the bonus of providing eggs. And an amenable Heterodontosaurus might make a perfect pet. Great with children. They could even have adapted to current-day habitats, dining on suburban dustbins.

Something like us

Perhaps the most advanced dinosaur at the time of the extinction was the Troodon which was "as cunning as a fox", according to palaeontologist Larry Witmer of Ohio University. They were small, upright, bi-pedal dinosaurs which lived in large groups. By studying the brain cavity, Witmer has found evidence they possessed good vision and even potentially had a brain structure compatible with problem-solving.

"If Troodon were around today, co-existing with humans, we'd probably call it a pest," says Professor Witmer.

With its substantial brain, long grasping hands and big eyes, could Troodon have evolved to become more intelligent? Evolutionary palaeo-biologist Dr Simon Conway Morris believes they could even have evolved along the lines of primates or humans.

"The human is extraordinarily well designed," he says. The whole arrangement is actually designed for a particular mode of life, which, as you can see looking around us, is incredibly successful. If it's such a good solution for us, is it so difficult to imagine it could be a good solution for a dinosaur, therefore a 'dinosauroid'?"

But most palaeontologists see the dinosauroid as an insult to dinosaurs.

"Dinosaurs probably would have continued along their dinosaurian trajectory, getting bigger brains and bigger eyes," says Kristi Curry-Rogers. "But I doubt seriously that any dinosaur would ever end up looking like a person, and it is fairly arrogant to think that the end point of all evolutionary trajectories should sort of emulate human beings."

If the asteroid had missed, there probably wouldn't be humans here today either to find out how it would have turned out. The impact that ended the golden age of the dinosaurs 65 million years ago made for an extremely bad dinosaur day but it was also a very good mammal day.

BBC

If for some reason the human race were to become infertile so that no more offspring is created, how long would it be before man was extinct? And what would happen to all that is left behind? How long would it take before the last traces were erased that would indicate our species once roamed this planet?

I know these are morbid questions, but nevertheless, there are always people who wonder about things like that (I for one), and I found some good material over the years to answer these questions.

Let’s start with the first question. Of course, we must hereby assume that cloning and artificial insemination is ruled out too. And to make it simple, let us take an easy date to start. If infertility were to suddenly hit the human race on the first day of 2008, then the last eggs were fertilised on the last day of 2007.  This in turn means that the last generation of humans will be born 9 months from that date. In Europe for example the average lifespan is 76 years for men, and around 81 for women. Of course there are always going to be exceptions and some will live longer. But it means that in about 80 years it will become a lot quieter in the cities. In parts of Russia and Africa where the average life expectancy is around 60, mankind will have checked out sooner. Sardinia has a lot of centenarians, more so than any other European nation, so I expect that the last few humans will be found there around a century later. By all accounts, when the year 2110 or 2112 starts, I’d be surprised if anyone made it that far.

Now on to the second and third question. Again, let’s keep it simple and chose a date as a starting point. 2100AD.

Change starts immediately. Within hours nature will start to eradicate all traces of our existence. Power stations and industry will cease and light pollution will end between 24 and 48 hours. Most, if not all, endangered species will start recovering. 3 months after the demise of Homo Sapiens, air pollution (nitrogen and sulphur oxides) lessens. Ten years on, and methane will be gone from the atmosphere.

Streets and cultivated fields will also start deteriorating fairly quickly. Within 20 years village streets and rural roads will be under a carpet of weeds and overgrown. Urban streets will take longer, but even in big cities plants would have taken over within about 50 years. Genetically manipulated crops will have disappeared after two decades, and wild growth will have taken over. Fish stocks will have recovered after half a century and all traces of Nitrates and phosphates will be gone out of fresh water.

Buildings will, like the streets, become overgrown with plants. Decay will be rapid, with wooden buildings first to go, due to assault by insects and weather. All such homes would be gone a century after we left the planet. Starting a century from the demise of man, bridges will begin to collapse. Two centuries, and our glass and steel tower blocks that dot our skylines will start to collapse one after another. Brick, stone and concrete structures will stand a little longer. Although the pyramids already stand for three millennia, by the next millennium there would not much be left apart from ruins. There is no one to make repairs and nature, in the form of frost, floods, storms, hurricanes etc will take its toll fairly soon.

250 years on, and dams would give way.

In nature, changes are rapid, the plant kingdom will be first to reclaim her rightful place, but animals will prosper as well. Five hundred years after mankind, corals will have regenerated; wildlife would thrive and reclaim earth. Around that time too, organic landfills will have mostly decayed.

A thousand years without the presence of man will see most brick, stone, and concrete buildings gone. Around the same time, carbon dioxide levels will be back to pre industrial levels.

Earth will follow its path through space, and we fast forward 20 000 years. All man made traces have vanished from this planet. However, there are still some around, probably covered by earth, weeds, and forests. 50 000 years on, plastics and glass will degrade. Only archaeological traces of mankind will be left.

Even though mankind is gone, even now his creations can still kill. Some man made chemicals only disappear after 200 000 years, and nuclear waste will remain deadly up to 2 million years. However, I assume it will be long buried by then.

Homo Sapiens has been around for roughly 150 000 years, our common ancestor maybe 5 to 6 million years. In contrast, dinosaurs ruled this planet for 165 million years, and before them there were others starting with the Cambrian explosion. In its short time on earth, our species sure made an impact, mostly the wrong one.

(sources: quest (Holland) & The Australia times, and myself.)