Read the passage and answer the questionLong ago prehistoric man began to domesticate a number of wild plants and animals for his own use. This not only provided more abundant food but also allowed more people to live on a smaller plot of ground. We tend to forget that all of our present-day pets, livestock, and food plants were taken from the wild and developed into the forms we know today.As centuries passed and human cultures evolved and blossomed, humans began to organise their knowledge of ...

Read the passage and answer the question

Long ago prehistoric man began to domesticate a number of wild plants and animals for his own use. This not only provided more abundant food but also allowed more people to live on a smaller plot of ground. We tend to forget that all of our present-day pets, livestock, and food plants were taken from the wild and developed into the forms we know today.

As centuries passed and human cultures evolved and blossomed, humans began to organise their knowledge of nature into the broad field of natural history. One aspect of early natural history concerned the use of plants for drugs and medicine. The early herbalists sometimes overworked their imaginations in this respect. For example, it was widely believed that a plant or part of a plant that resembles an internal organ would cure ailments of that organ, Thus, an extract made from a heart- shaped leaf might be prescribed for a person suffering from heart problems.

Nevertheless, the overall contributions of these early observers provided the rudiments of our present knowledge of drugs and their uses

The word “this” refers to ……….