Question

Laboratory Activities

The Scientific Method and Measuring in the International System of Units (SI)

Laetoli Footprint Study (used with permission from Amy Hopkins)

Background

In 1976, a team of scientists working under archaeologist-paleontologist Dr. Mary Leakey discovered the fossilized tracks of an early (now extinct) human. Archaeologists thought an early human, called Australopithecus, could have made the fossil footprints. Two years earlier, in 1974, an almost complete Australopithecus fossil skeleton had been found, which scientists nicknamed “Lucy”. It was not immediately known if the fossil footprints found by Dr. Leakey’s team were made by an individual related to “Lucy”, but the age of the fossil footprints, their location, and their structure seemed to indicate that they were indeed related.

The fossil footprints were found in Africa, at a site named Laetoli, which is located in Tanzania. The footprints were made 3.5 million years ago in, what was at the time, damp volcano ash. A layer of volcanic ash deposited by a volcanic eruption covered the ground. After the ash settled, it rained lightly and the ash layer took on the consistency of damp sand. Three individuals walked upon this ash, leaving their footprints. These footprints were later covered by more ash from later volcanic eruptions, and eventually became fossilized.

Research

The scientists working at the Laetoli site wondered if they could tell anything about the individuals that had made the footprints by studying the footprints themselves. The footprints looked as though humans made them. The impressions of the big toe, the rounded heel, and other characteristics of a human footprint were clearly visible. They could measure the prints (their length, width, distance apart, etc.) and from this data perhaps tell something about the individuals that made the prints.

A hypothesis was put forward: if there is a relationship between the length of a person’s foot and that person’s height, we could predict how tall a person is by knowing the length of their foot. If this is true, we could use the footprints at Laetoli to determine the height of the individuals that made the prints.

Exercise

An important part of science is finding answers to complex questions. Scientists look for relationships, or patterns in nature, that can be used to make predictions in order to solve problems. In this exercise, you will look to see if there is a relationship between a person’s foot length and their height. If such a relationship exists, you can predict how tall a person is just by knowing the length of their foot.

Answer 1

This research exercise has two parts- proposal of a hypothesis of a correlation between foot length and height and its quantification by data acquired from a population, and generating a hypothesis to back the correlation. Several pieces of research done in the area propose that foot length is proportional to height as it ensures a proper balance of the body. However, both have various determinants- gender, genetics, health, and environment. Quantification of this correlation in a study published in International Journal of Biological and Medical Research by Pawar and Dadhich (Int J Biol Med Res. 2012; 3(3): 2232 -2235) concludes that height is 6.5 times the length of the foot. Such can be used to calculate, to some extent predict the height of the ancient human whose footprint was found by Dr.Leakey's team.