5 facts you probably didn't know about balls. You're welcome.

The study, a first of its kind, has shown that fathers with smaller sacks are more likely to be involved in ‘hands-on care of their toddlers’, and that blokes with bigger balls are more likely to be poor parents and promiscuous.

Dr James Riling, from the Emroy University in Atlanta, took 70 fathers aged between 21 and 43 and asked them bear their balls in the name of science.

After measuring the gentlemen’s grapes as a pear, and then surveying their loved ones to find out how they behaved at home, researchers noticed a trend.

When parenting scores rose, the testes size fell.

Are you laughing yet?

The correlation stayed the same even when the researchers took into account the men’s height and natural testosterone levels. Or in more scientific terms:

The findings showed that both testosterone levels and testes size were inversely correlated with the amount of direct paternal caregiving reported by the parents in the study.

In the next stage of the study, each fella was asked to pull up their jocks and get linked too a brain scanner. They were then shown a random selection of photos of other adults, unrelated children and then their own.

When a photograph of their own child flashed up, men with smaller sacks, showed more activity in the ‘ventral tegmental area’ – or, the section of the brain that’s linked to nurturing.

At its core, the paper says that these finding help prove that males are subject to an evolutionary principal called the ‘life history theory’.

In this latest interpretation of the theory, the researchers say that this study proves that males are forced to make a trade-off between investing time and effort into mating vs. investing time into looking after raising offspring.

As the study put it:

Life History Theory suggests that evolution optimises the allocation of resources toward either mating or parenting to maximise fitness.

“Our study is the first to investigate whether human anatomy and brain function explain this variance in parenting effort,” says Jennifer Mascaro, who led the study as a post-doctoral fellow in the Rilling lab.

That tree won’t make a good father.

In a completely unscientific translation, and a more Discovery Channel interpretation, it’s proposed that blokes are either born a wombat – who eats, roots and leaves (say that really fast without laughing) – or a papa penguin – one of the few male animals in the kingdom who actually pull more weight than the women when it comes to parenthood.

You can read the full studies summary here, and some other international commentary on the yarn bag investigation here and here.

Let’s just hope this study isn’t one big balls up.

And just to brighten up your day, here are five facts you may not have known about a man’s crown jewels

1. Testicles have their own thermostat built inside. When it’s chilly, they drop. When they need warmth, they get closer to the body to borrow some heat. See, they really do have a mind of their own.

2. The left testicle often hangs lower than the right testicle.

3. During sex, testicles can double in size.

4. Testicles don’t have the normal protection that other organs are lucky enough to have, making them particularly vulnerable and sensitive.

5. An octopus’s testicles are in their head.

So what do you make of all this study? Can you see the logic or does it just suck balls?