How long can humans actually live for?

The truth is, scientists say, we just don't know.

A study published in the journal Nature last year concluded that the upper limit of human age is peaking at around 115 years - a threshold crossed by super-centenarians like Italian woman Emma Morano, who recently died age 117, and Jeanne Calment of France, who famously lived to be 122.

But a new study featured in the same journal, in which biologists at Canada's McGill University analysed the lifespan of the longest-living individuals from the US, the UK, France and Japan for each year since 1968, found no evidence yet for such a limit.

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They did however point to trends of increasing maximum lifespans that would likely continue into the future.

In 1920, for example, the average newborn Canadian could expect to live 60 years; a Canadian born in 1980 could expect 76 years, and today, life expectancy has jumped to 82 years.

Yet it was still impossible to predict exactly what future lifespans in humans might look like, and some scientists argue that technology, medical interventions and improvements in living conditions could all push back the upper limit.

"It's hard to guess," study co-author Dr Siegfried Hekimi said.

"Three hundred years ago, many people lived only short lives. If we would have told them that one day most humans might live up to 100, they would have said we were crazy."

Social situations mean we're not pitch perfect

People tend to change the pitch of their voice depending on who they are talking to, scientists say. Photo / 123RF
People tend to change the pitch of their voice depending on who they are talking to, scientists say. Photo / 123RF

People tend to change the pitch of their voice depending on who they are talking to.

Psychology research just published in PLOS ONE, put participants through a simulated job interview task and discovered that individuals' vocal characteristics - particularly pitch - are altered in response to people of different social status.

Regardless of self-perceived social status, people tend to talk to high-status individuals using a higher pitch.

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"A deep, masculine voice sounds dominant, especially in men, while the opposite is true of a higher pitched voice," said study author Dr Viktoria Mileva, of the UK's University of Stirling.

"So, if someone perceives their interviewer to be more dominant than them, they raise their pitch."

This could be a signal of submissiveness, where we showed the listener that you we were not a threat, or to avoid possible confrontations.

"These changes in our speech may be conscious or unconscious but voice characteristics appear to be an important way to communicate social status.

"We found both men and women alter their pitch in response to people they think are dominant and prestigious."

The researchers also found that participants who think they are dominant - who use methods like manipulation, coercion and intimidation to acquire social status - are less likely to vary their pitch and will speak in a lower tone when talking to someone of a high social status.

Individuals who rate themselves as high in prestige - they believe people look up to them and value their opinions, thereby granting them social status - do not change how loudly they are speaking, no matter who they are speaking to.

This could signal that they are more calm and in control of a situation.

"Signals and perceptions of human social status have an effect on virtually every human interaction, ranging from morphological characteristics - such as face shape - to body posture, specific language use, facial expressions and voices," Mileva said.

"Understanding what these signals are, and what their effects are, will help us comprehend an essential part of human behaviour."

Cockatoos play it cool

The shy and elusive palm cockatoo, iconic to Cape York Peninsula in far North Queensland, is adept at playing the drums. Photo / 123RF
The shy and elusive palm cockatoo, iconic to Cape York Peninsula in far North Queensland, is adept at playing the drums. Photo / 123RF

While songbirds and whales can belt out a musical tune, few species recognise a beat.

But the shy and elusive palm cockatoo, iconic to Cape York Peninsula in far North Queensland, plays the drums and crafts the sticks.

"The large smoky-grey parrots fashion thick sticks from branches, grip them with their feet and bang them on trunks and tree hollows, all the while displaying to females," said Australian National University researcher Professor Rob Heinsohn, whose observations have just been published in the journal Science Advances.

"The icing on the cake is that the taps are almost perfectly spaced over very long sequences, just like a human drummer would do when holding a regular beat."

Heinsohn said the palm cockatoo's ability to drum has been known for a long time but this is the first research to secure the footage to analyse it.

This was slowly acquired over the seven-year study by patiently stalking the birds through the rainforest with a video camera.

"Each of 18 male palm cockatoos, known for their shyness and elusiveness, was shown to have its own style or drumming signature," he said.

"Some males were consistently fast, some were slow, while others loved a little flourish at the beginning.

"Such individual styles might allow other birds to recognise who it is drumming from a long way away."

The palm cockatoo drumming was part of the species courtship ritual that involved a lot of calls and movements to attract a mate.

The research was part of a broader study of the palm cockatoo's conservation needs on the Cape York Peninsula, where they suffer low breeding success and loss of habitat due to mining activity.