During What Time Period Did Hominid Brain Size Begin To Expand Rapidly?

Bigger Brains: Complex Brains for a Complex World

Endocasts of Homo erectus, (left) and Homo sapiens (right) — Endocasts of Homo erectus (left) and Human being sapiens (right) illustrate rapid increase in brain size.
(James Di Loreto, & Donald H. Hurlbert, Smithsonian Institution)

As early humans faced new environmental challenges and evolved bigger bodies, they evolved larger and more complex brains.

Large, complex brains can process and store a lot of data. That was a big advantage to early humans in their social interactions and encounters with unfamiliar habitats.

Over the course of human evolution, brain size tripled. The modern human brain is the largest and about complex of whatsoever living primate.

Brain size increases slowly

From six–ii one thousand thousand years ago

During this fourth dimension catamenia, early humans began to walk upright and make simple tools. Brain size increased, but only slightly.

Encephalon and body size increase

From 2 1000000–800,000 years agone

During this fourth dimension period early humans spread around the globe, encountering many new environments on different continents. These challenges, along with an increment in trunk size, led to an increase in brain size.

Brain size increases rapidly

From 800,000–200,000 years ago

Human brain size evolved almost rapidly during a fourth dimension of dramatic climate change. Larger, more complex brains enabled early on humans of this fourth dimension catamenia to interact with each other and with their surroundings in new and different ways. Equally the surroundings became more unpredictable, bigger brains helped our ancestors survive.

Why the sudden increase in brain size?

Graphs showing changes in climate and changes in braincase volume — Graphs showing changes in climate and changes in braincase book. Courtesty of Karen Carr Studios
(© Copyright Smithsonian Institution)

The top graph shows how Earth's climate has fluctuated over the past 3 million years. Notice how much the fluctuations increased between 800,000 and 200,000 years ago. To construct this graph, scientists studied fossils of tiny organisms found in body of water sediment cores.

The bottom graph shows how encephalon size increased over the past 3 one thousand thousand years—especially betwixt 800,000 and 200,000 years ago. A large brain capable of processing new information was a large advantage during times of dramatic climatic change. To construct this graph, scientists measured the brain cavities of more 160 early man skulls.

Testify of ancient brains

Endocasts are replicas of the insides of early and modern human braincases. They represent the size and shape of the brains that once occupied the braincases.

How are endocasts fabricated?

Brains do not fossilize. They deteriorate, leaving a crenel inside the braincase.

Sometimes sediments make full the cavity and harden, making a natural endocast. Scientists also make artificial endocasts to written report, like the ones in a higher place.

To obtain an accurate measure of brain size, scientists remove an endocast from the braincase and record its volume, or use CT scanning to measure out the inside of the braincase.

Compare Your Encephalon with a Chimpanzee's

Humans are primates, and chimpanzees are our closest living relatives.

The brains of the earliest humans were like in size to those of chimpanzees. But over fourth dimension, human being and chimpanzee brains evolved in several unlike and of import means.

Speed of Growth

chart of Chimpanzee brain growth rapidly before birth. — Chimpanzee brains grow quickly before birth. Growth levels off very before long afterwards birth. Paradigm courtesy of Karen Carr Studio.
(© Copyright Smithsonian Institution)

chart of Human brain growth showing growth rapidly before birth through the first year and into childhood — Human brains grow speedily before nascency through the first year and into childhood. Image courtesy of Karen Carr Studios
(© Copyright Smithsonian Establishment)

Connections

A chimpanzee's temporal cortex has less white thing, reflecting fewer connections between nervus cells.

Humans have far more white matter in the temporal cortex, reflecting more connections between nervus cells and a greater ability to process data.

Size

Average weight of adult chimpanzee brain: 384 g (0.85 lb)

Average weight of modern human brain: i,352 chiliad (2.98 lb)

Benefits and Costs of a Large Encephalon

graphic of silhouettes of two men and text: Brain Size 2% and Brain's Energy Needs 20% — Encephalon weight versus energy requirements. Paradigm courtesy of Karen Carr Studios
(© Copyright Smithsonian Institution)

Benefits

The mod human brain can:

- store many decades worth of data;

- collect and process information, then deliver output, in split up seconds;

- solve problems and create abstract ideas and images.

Information technology tin also do much more.

Costs

- A large encephalon gobbles up energy. Your brain is 2 percentage of your trunk'southward weight but uses 20 pct of your oxygen supply and gets xx pct of your blood flow.

- Large brains mean large heads, making childbirth more difficult and painful for man mothers than for other primates.