Having one left-handed child is relatively common, occurring in around 10% of the population. But what are the chances of having multiple left-handed kids? Let’s take a closer look at the genetics and statistics surrounding left-handedness in families.
What causes left-handedness?
Left-handedness is believed to be caused by a complex interaction between genetics and environment. Specific genes have been associated with left-handedness, but no single “handedness gene” has been identified. Instead, handedness seems to be influenced by multiple genes that each make small contributions to the likelihood of being left-handed.
In addition to genetics, factors like exposure to hormones in the womb, birth complications, and early childhood experiences may influence handedness. So while left-handedness does tend to run in families, there are many factors at play.
What are the chances of having 2 left-handed kids?
If one parent is left-handed, the chances of having a left-handed child are around 26%. With two left-handed parents, the chances rise to around 36%. Here are some statistics on the likelihood of multiple left-handed kids based on parental handedness:
| Parental Handedness | Chance of 1 Left-Handed Child | Chance of 2 Left-Handed Children |
|---|---|---|
| Neither parent left-handed | 10% | 1% |
| 1 parent left-handed | 26% | 7% |
| Both parents left-handed | 36% | 13% |
As you can see, the chances of having multiple left-handed kids goes up significantly if one or both parents are left-handed themselves. However, it is still relatively uncommon to have 2 left-handed children.
Why are the chances higher with left-handed parents?
The increased chance of left-handedness with left-handed parents can be explained by genetics. Although no single “handedness gene” has been found, studies have identified regions on chromosomes 2, 10, and 12 that are associated with left-handedness.
Parents pass down genetic material to their children, so left-handed parents are more likely to pass down some of these genetic variations linked to left-handedness. Each child has around a 26% chance of inheriting left-handed genetics from a left-handed parent.
Role of random chance
Genetics don’t fully determine handedness though. Even with two left-handed parents, there is still only around a 1 in 3 chance of a child being left-handed due to the complex interaction between genetics and environment.
There is also an element of random chance, just like tossing a coin. Getting two left-handed kids in a row would be akin to flipping a coin twice and getting heads both times. Unlikely by chance, but certainly possible.
What factors make having 2 left-handed kids more likely?
While having 2 left-handed kids is relatively uncommon on average, there are some factors that can make it more likely:
- Both parents being strongly left-handed (not ambidextrous)
- Left-handedness running strongly in the family
- The couple having several children (more chances for left-handed kids)
- Male children – left-handedness is more common in males
- Birth factors like prematurity or trauma
So while the baseline chance is around 1-7%, families with multiple strong left-handedness traits could see higher odds of having 2 or more left-handed children.
Are rates of left-handedness increasing?
Over the past century, left-handedness has become more socially accepted in many cultures. In the past, left-handed children were often forced to switch to using their right hand. Today, left-handers face less stigma and pressure to change their handedness.
This increase in acceptance has led to an increase in reported rates of left-handedness over the past several decades. More people are freely expressing their natural left-handedness rather than feeling pressure to switch hands.
However, it’s unlikely there has been any dramatic increase in the genetic predisposition for left-handedness. Rather, the genes were always present in the population, just not always expressed. So while social acceptance has enabled more left-handers to publicly identify as such, the actual genetic likelihood has probably not increased significantly.
Reported rates over time
| Year | Reported Left-Handedness |
|---|---|
| Early 1900s | 3% |
| 1920s-1930s | 4% |
| 1970s | 8% |
| 2000s | 10-13% |
As stigma decreased over the 20th century, reported rates of left-handedness increased. But the actual genetic likelihood has likely remained stable over time.
Chances of 2 left-handed kids in the future
It’s unlikely that the actual rates of the left-handed genetic traits will increase substantially in the future. But with continued acceptance, more left-handers may openly identify as such rather than masking their handedness.
This could lead to a larger pool of people with genetic left-handed tendencies having children. If so, the chances of left-handed offspring, including multiple left-handed kids in a family, could slowly increase further.
However, dramatic increases are improbable since handedness is a complex genetic trait involving many genes. The baseline rate of left-handedness is likely to remain around 10% overall. The chance of having 2 left-handed kids will still be fairly low for the average couple.
Impact of having 2 left-handed kids
While having 2 left-handed kids is uncommon, it shouldn’t have major implications for a family. Left-handedness is just a natural variation, not something to worry about. Some considerations with multiple left-handed kids include:
- Ensuring kids have access to left-handed school supplies, sports equipment, etc.
- Being aware that lefties struggle more with smudging ink, spiral notebooks, scissors and other right-handed biased tools
- Teaching kids adaptability with using both hands for certain tasks
- Letting children express their natural handedness rather than forcing right-handed use
With acceptance and accommodation, being left-handed is mostly just an interesting difference, rather than a disadvantage. Families with multiple left-handed kids will adapt well.
Conclusion
While one left-handed child is relatively common at around 10% of the population, having two left-handed children in a family is much rarer, occurring only about 1-7% of the time on average. The chances go up somewhat if one or both parents are left-handed, due to the genetic influence. But because handedness is a complex genetic trait, getting two left-handed kids is still statistically uncommon and partially due to random chance.
Rates of reported left-handedness have increased over the 20th century as stigma declined, but the actual genetic likelihood has probably remained stable. The chances of having two left-handed children in the future are unlikely to change dramatically. Though less stigma could lead to small increases in families with multiple left-handed kids. Regardless, for most families, having two left-handed children will remain relatively uncommon.