york counting feels utterly effortless to adults who are unlikely to even remember when or how they picked up this useful apparently automatic skill yet when you think about it counting is a remarkable invention it helped early humans to trade apportion food and organise fledgling civilisations laying the foundations for life as we know it todaybut a sensitivity for numbers isnt uniquely human tiny guppies and honeybees as well as hyenas and dogs have been found to perceive and act on numerical stimuli so responding to numbers is an evolved trait we seem to share with some animals as well as a skill were taught in some of our first lessonsas a researcher in numerical cognition im interested in how brains process numbers humans and animals actually share some remarkable numerical abilities helping them make smart decisions about where to feed and where to take shelter but as soon as language enters the picture humans begin outperforming animals revealing how words and digits underpin our advanced mathematical worldtwo number systemswhen we think of counting we think of one two three but that of course relies on numerical language which young humans and animals do not possess instead they use two distinct number systemsfrom as young as ten months old human infants are already getting to grips with numbers but theres a limit to their numerical skills they can only detect number changes between one and three as when one apple is removed from a group of three apples this skill is shared by many animals with significantly smaller brains such as fish and beesthis early numerical system helping infants and animals perceive the number of a small set of objects without having to actually count probably relies on an internal attentional working memory system that is overwhelmed by numbers above around threeas we grow up we become able to estimate far higher numbers again without needing to refer to language imagine youre a hungry huntergatherer you see two bushes one with 400 redcurrants and the other with 500 its preferable to approach the bush with the most fruit but its a big waste of time to count the berries on each bush individuallyso we estimate and we do this with another internal number system specialised for approximating large numbers imprecisely the socalled approximate number system given that theres a clear evolutionary advantage for those who can quickly pick the most bountiful food source its unsurprising that fish birds bees dolphins elephants and primates have all been found to possess an approximate number systemin humans the precision of this system improves with development newborns can estimate approximate differences in numbers at a ratio of 13 so will be able to tell a bush with 300 berries has more berries than one with 100 come adulthood this system is honed to a 910 ratioeven though these two systems appear in a range of animals including young humans this doesnt necessarily mean that the brain systems behind them are the