大停顿//  小停顿/  bold 加强语气

Life expectancy预期寿命 has increased dramatically戏剧性的,大大地 in the last century.// Most people these days如今 will live for over 70 years old./ This is more than double翻倍 the lifespan寿命 of the average human in the 17th century.// We can attribute归功 our longevity长寿 to advances进步 in medicine and lifestyle./ While everyone agrees that living longer is wonderful,/ overpopulation人口过剩 is becoming a serious environmental concern环境问题.