When mass murders happen in a place like the US, despite the fact that they are no more prevalent than most countries and murders have plummeted as gun ownership rose, the simplistic answer is 'guns' - when murders happen in Canada or France, where gun ownership is heavily restricted, the answer is not so convenient. 

It may not be guns forcing people to kill people, it may be attachment to an 'overvalued idea' - and it may become more common.

Zehaf-Bibeau, the Islamist convert who murdered a Canadian military reservist on duty in Ottawa, represents a type of attacker rarely discussed--a person so obsessed with an overvalued idea that it defines their identity and leads them to commit violence without regard for the consequences.

Air Force reservists based in the U.S. who worked after the Vietnam War in C-123 aircraft that sprayed Agent Orange during the war could have experienced adverse health effects from exposure to the herbicide, says a new report from the Institute of Medicine. The reservists who served in the contaminated C-123s experienced some degree of exposure to the toxic chemical component of Agent Orange known as TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), and it is plausible, in some cases, that the reservists exceeded TCDD exposure guidelines for workers in enclosed settings.

Gine Roll Skjaervoe at the Norwegian University of Science and Technology's (NTNU) Department of Biology has studied church records from the period 1750-1900 and looked at life history variables: how old were women when they had their first child, and their last? How many years passed between the birth of each child, and how many of these children survived? How many of these children were in turn married and had children?

All told, she studied information from more than 9,000 people listed in the church records she examined.

A man-made form of insulin delivered by nasal spray may improve working memory and other mental capabilities in adults with mild cognitive impairment and Alzheimer's disease dementia, according to a pilot study led by researchers at Wake Forest Baptist Medical Center.

The study's subjects were 60 adults diagnosed with amnesic mild cognitive impairment (MCI) or mild to moderate Alzheimer's dementia (AD). Those who received nasally-administered 40 international unit (IU) doses of insulin detemir, a manufactured form of the hormone, for 21 days showed significant improvement in their short-term ability to retain and process verbal and visual information compared with those who received 20 IU does or a placebo.

The debate over policy implications of climate science can have no clear winners - everyone claims science is on their side and that scientists on the other side are misguided. Though both sides are experts at framing - CO2 is good for us in any quantity, skeptics are all dupes of Big Oil - one was clearly taking it to the next level: In 2000, Professor Paul Crutzen, who won the 1995 Nobel Prize in Chemistry with Mario Molina and Sherwood Rowland for work on ozone, said humankind's impact was so drastic it has changed the actual geology of Earth and since then environmentalist have been promoting Crutzen's new Epoch - the Anthropocene - as a distinct chapter in the Earth's geological history.

Scientists have extracted DNA from mysterious marsupial megafauna that roamed Australia over 40,000 years ago -  Australia's extinct giant kangaroos.

The team extracted DNA sequences from two species: a giant short-faced kangaroo (Simosthenurus occidentalis) and a giant wallaby (Protemnodon anak). These specimens died around 45,000 years ago and their remains were discovered in a cold and dry cave in Tasmania.

Relatively good preservation conditions in the cave allowed enough short pieces of DNA to survive so researchers could reconstruct partial "mitochondrial genomes" - genetic material transmitted from mother to offspring and widely used to infer evolutionary relationships.