Oxygen in the Earth’s atmosphere is necessary for complex forms of life, which use it during aerobic respiration to make energy. The levels of oxygen dramatically rose in the atmosphere around 2.4 billion years ago, and speculation is that is when organisms called cyanobacteria, which perform the same type of organic photosynthesis that all plants do today, first evolved, and  could perform oxygen-producing (oxygenic) photosynthesis.

Perhaps cyanobacteria could have evolved before 2.4 billion years ago but something prevented oxygen from accumulating in the air.

The transition from ape-like shuffling to upright walking (bipedalism) as we do has long fascinated scientists. Why did it happen? When? 

The second question is a little closer to being solved. An analysis of 3.6 million year old hominin footprints in Tanzania suggests our ancestors evolved the hallmark trait of extended leg, human-like bipedalism substantially earlier than previously thought. Many millions of years before humans. Like the chicken and the egg, there is a clear science answer about which came first even if philosophers are baffled.

In the 1800s, critics of evolution insisted there had to be fossil evidence for everything, which neglected the idea that fossilization is already difficult, finding the fossil is even more difficult, and something like an eye will not fossilize at all.

But detractors who insisted they would not accept evolution until they found a "missing link" between modern humans and ancestral primates would be moving the goalposts once again, because a fossil of an ancient hominin individual from Siberia had a Neanderthal mother and a Denisovan father. 
A technique used to produce stone tools that were first found 500,000 years ago is likely to have needed a modern human-like hand, according to new research.

The technique is called 'platform preparation' - preparing a striking area on a tool to remove specific stone flakes and shape the tool into a pre-conceived design - and without the ability to perform highly forceful precision grips, our ancestors would not have been able to produce advanced types of stone tool like spear points. 

Platform preparation is essential for making many different types of advanced prehistoric stone tool, with the earliest known occurrence observed at the 500,000-year-old site of Boxgrove in West Sussex, UK.
The 2017 hurricane season was one of the most expensive in the Atlantic Ocean region. Hurricane Harvey hit in mid-August 2017, followed just a few weeks later by Hurricane Irma and Hurricane Maria in September. Each of these storms had winds in excess of 125 mph, with Irma up to 170 mph. Damage from totals for the hurricane season topped $282 billion. 
It isn't just human adults who regard youth as disease factories, in many species the young are often more susceptible to infection than adults, even after accounting for prior exposure to infection.

Evolution has an explanation for that. But like a lot of things in evolution, it may seem puzzling.

It shouldn't make sense, since dying young or becoming infertile due to infection means organisms will be unable to reproduce, but many species may have evolved to prioritize growth over immunity while maturing. And that complexity may be why immunity varies with age in different species.
From a young age, children have a nuanced understanding of how free markets work. A new study in Child Development indicates that children as young as five incorporate market concerns—the idea that what you get is in line with what you give or offer—into their decision making, and increasingly do so with age.

Some people think children are innately selfish, they want to get goodies for themselves, while others insist they are more communist, each will do more to help those who can't or won't do enough. By studying how children engage in different types of exchanges, researchers hope to discern the origins of these behaviors, as well as their developmental course.
It sounds gross to humans - unless you read those "Twilight" books in which case maybe it's sexy - but a lot of animals consume blood.  That's right, even your cat familiar. 

The question is why? Blood is actually a poor source of energy. It consists of 78 percent liquid and what is left is 93 percent proteins and only one percent carbohydrates (1). Blood provides very little in the way of vitamins. Not only that, a blood-based diet exposes animals to blood-borne pathogens.

And yet some bat species (order Chiroptera) feed exclusively on blood and have managed to survive evolution that should have killed them, and their reliance on low-grade nourishment, off.
How do you miss an organ important for the function of all organs, most tissues and the mechanisms of most major diseases? Easy, you don't look for it. 

In graduate school, I earned beer money by modeling for life drawing classes in various art departments. (Don’t judge, grad school doesn’t pay well and beer isn’t free.) In the long hours standing around, I would survey the room and count how many of the aspiring artists were left-handed. Later in my career, I did the same thing — counting lefties, not standing around naked — in the biology classes I taught.

Funny thing, in any given class, around 10 per cent of the students were lefties. It turns out this is true for all human populations, not only middle-America university classes. Globally, about 90 per cent of people are righties. But why?