One study of children in Bristol showed differences in growth depending on whether their grandfathers had smoked before the age of 11. Their bodies probably reacted defensively, adapting in the short term by changing the genes for the next few generations, or until the “danger” had passed, a so-called “soft inheritance” running in parallel to slower-acting evolutionary forces.
揭示这类代际效应的实体实验不可能在人身上进行，因此必须利用历史和观察数据。一项针对布里斯托（Bristol）儿童的研究表明，成长差异取决于祖父辈是否在11岁以前吸烟。他们的身体可能会出现防御反应，通过改变下几代的基因实现短期适应，或者在“危险”过去之前，所谓的“软遗传”和反应较慢的进化力量一起起着作用。