Scared of Big Brother? You should be!
This is Sandra Tsing Loh, with the Loh Down on Science.
Meet Ian Richard, from the University of Sheffield, UK. Richard reviewed church records from Eighteenth- and Nineteenth-century Finland. He found that children born after a brother were almost always smaller than their elder sibling. This held true even into adulthood.
Post-brother siblings were also less likely to have children of their own. When they DID, the kids came LATER, and there were fewer.
The outcome was the same across social classes— even when the offending brother actually died in infancy.
This means a purely biological effect is at work.
Most likely? Boy fetuses leech so many resources off Mum she has less to give the next baby.
And the hand-me-downs! So big, so baggy!
Reference: Lawson, D. W., & Mace, R. (2008). Sibling configuration and childhood growth in contemporary British families. International journal of epidemiology, 37(6), 1408–1421. https://doi.org/10.1093/ije/dyn116