Not just the power house of the cell.

Biology: Mitochondrial DNA

 In 1987, a group of scientists published a paper about mitochondrial DNA and the common mitochondrial ancestor that humans all over the world share. Mitochondrial DNA is different from nuclear dna and is only inherited maternally (from mothers, because sperm cells do not contain mitochondria). The DNA stays relatively unchanged throughout generations and the only source of variation is mutation (which occurs at a slow and steady rate). Human mitochondrial DNA codes for around 37 genes (compared to nuclear DNA which codes for around 30,000 genes). The mitochondrial DNA that the scientists tested was from all over the world and can all be traced back to a singular woman who lived (probably in Africa) around 170,000 years ago. This woman is nicknamed “mitochondrial Eve”. The average differences in the mitochondrial dna of the participants of the study was 9.5. The DNA difference within a group (eg. just in Europe) is higher than the difference between groups (eg. between Europe and Asia). It was also found that Africa had the highest number of mutations (probably because that is where the lineage started) and Australia had the lowest number of mutations (because humans immigrated there relatively recently). They claimed in their conclusion that a larger sample size would have given a more definitive answer about the lineage of mtDNA.

That awkward moment when your fossil gets found in a cave.

 In level three biology, we have been learning about human evolution. As a fun add on, we have learnt about a random species found in a cave system in south Africa. This species is an interesting thing, where it contains both human like features and ape like features. Another annoying challenge is the lack of surrounding rock and other substance, that makes working the age of this species a bit difficult. 

Homo Naledi

Australian museum (2019)

https://australian.museum/learn/science/human-evolution/homo-naledi/

Whilst on a cave expedition in 2013, two cavers found themselves in an unexplored part of the ‘rising star’ caving system (in south Africa). In this unexplored chamber, there were many human like fossils. This was a huge scientific discovery. The call went out for more cavers (who were small enough to fit through a narrow part of the cave. The 6 most qualified people who were chosen to collect the fossils were all young women. ‘Naledi’ comes from the word for ‘star’ in the local Sotho language. The strange thing about Homo Naledi is the combination of advanced human like features (shape of skull, hand structure, foot structure and the bottom half of the pelvis) along with earlier features (small stature, small cranial capacity, robust collar bones and arm bones which suggest climbing). The remains were also found in a cave, but there is no evidence that they were dragged down by predators. It is also very unlikely that the amount of homo naledi found in the caves just got lost and died. It is more likely that they were buried, in a ritualistic manner. This would suggest the potential of abstract thought and rituals within the species. Then again, its not like we can go back and ask them :)