The Evolution of The Human Head

Introduction:
This analysis examines the evolution trends of the human head by focusing on factors that affect and/or can be affected by cranial capacity. Cranial capacity (i.e: the volume of the head) provides deep insights on how humans evolved in various aspects such as: bipedalism, dietary preference, cognitive ability etc.

Objective:
Study the evolutionary trend of the human head across ancient species to modern species by looking at the determining features of cranial capacity, measured in centimetre cubic (cm3).

Data:
The dataset (Biological Data Of Human Evolution Data Sets) is sourced from Kaggle. Data cleaning and wrangling were done using Python libraries. The majority of the samples in this dataset were from the Africa region, followed by equivalent portion from Europa and Asia regions.
This study focused on the following features: incisor size, jaw shape, torus supraorbital, prognathism and foramen magnum position.
The time frame unit used in this study is million years ago (MYA). Keep in mind that the larger the unit of MYA, the more ancient the species is.

Finding:
1. Cranial capacity trends
The dataset suggested that cranial capacity has steadily increased in volume over time, with the maximum recorded is around 1400 cm3 which was observed from 1.2 MYA onwards, whilst the minimum around 80 cm3, observed close to 8 MYA. There was a stagnant period from 6-8 MYA, but an increasing trend was observed from 5 MYA. However, around 1 MYA, there is record of a species, albeit a hominin, with a small cranial capacity of around 180-420 cm3.

2. Cranial capacity on height trends
There is also a positive correlation between cranial capacity and height, with possible regional influence. Generally, individuals with larger cranial capacity (i.e: larger head) is expected to also be bigger in size (i.e: greater height). The specimen from Africa comprises of a really wide range of size ( 100 - 1380 cm3 for 80 - 1400 cm in height). Meanwhile, specimens from Europa tend to be larger (850 - 1420 cm3 for up to 180 cm in height), whilst those from Asia somewhat occupies a wide range (180 - 1200 cm3 for 100 - 160 cm in height). The regional limitation in this dataset is due to Africa disproportionately outnumbers Europa and Asia regions.

3. Incisor size
Whilst small incisor is the most commonly found in the dataset, it is the very small incisor that is strongly related to having larger cranial capacity. This suggests that the more modern species has access to tools/technology to cook and process raw food material, thus having no need for larger incisor.

4. Jaw shape
U-shape jaw has the highest frequency in the dataset, but only made appearance about 5 MYA. U-shape jaw has been consistently co-observed with increasing cranial capacity - only until recently (1 MYA) where they are observed amongst individuals with lower cranial capacity. As expected, modern jaw dominates the current jaw shape, concurrent with larger cranial capacity as well.

5. Torus supraorbital (eyebrow ridge)
The (presence or absence of) eyebrow ridge is believed to be a direct indication of a species' dietary habit. The ridge functions to resist bending stress concentrated over the eyes during anterior biting and that its development is proportional to the amount of such stress which cannot be resisted by the unadorned frontal bone.
The dataset found that flat supraorbital seems to coexist most commonly with higher cranial capacity. This is consistent with modern humans, almost no supraorbital in combination with larger cranial capacity. The more ancient a species, the more they conform to a pattern: the more protruding the supraorbital, the lower the cranial capacity.

6. Prognathism
Prognathism is the protrusion of the mandible (lower jaw). Its significance is understood to provide space for more muscle for chewing, which is expected in species that eats tough or unprocessed food material. The disappearance of prognathism is an indication of a more modern and evolved species.
The dataset backed this hypothesis. Ancient species, from 1.8 - 8 MYA, displayed a varying high degrees of prognathism. Species with reduced prognathism was observed around 2 MYA, whilst those with complete absence of prognathism emerged about 1 MYA.

7. Foramen magnum position
Foramen magnum is the opening in the skull where nervous system from the body is connected to the brain via spine. A posterior foramen would not allow for an individual to stand upright and hold their head up comfortably. Therefore, posteriorly located foramen is more likely to be associated with quadrupedals.
Individuals with semi-anterior foramen showed high possibility of evolving into a bipedal. This is consistent with modern humans, which indeed do stand on two feet rather than four

Conclusion:
The dataset suggests that all the investigated determining features of cranial capacity evolution are consistent with theories.