Human beings have more than 98% similarities in genomes with chimpanzees; thus the common comparison between them. The many similarities in their biology, life history, and behaviour are accounted for, and yet they still have many striking differences. The similarities between chimpanzees and human DNA led Charles Darwin in 1871 to predict that Africa is the place where human lineage branched off from the other animals. Human beings have apparent similarities with chimpanzees such as two eyes, four limbs, and that they are warm-blooded.
Chimpanzees and humans have many similarities in their biochemistry; they have almost the same organs and functions. However, human beings have higher intelligence, attention span, and can communicate with other human beings, unlike the chimpanzees. The fundamental differences between humans and chimpanzees are reflected in the 2% differences in their genomes. The 2% makes a significant difference; it is what separates human beings from chimpanzees. The purpose of this annotated bibliography is to summarize the literature on what differentiates human beings from chimpanzees despite their 98% similarities in their genomes. Researchers have conducted extensive studies to identify the difference in cognitive abilities and brain structure that make human beings more advanced in comparison to chimpanzees.
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Mora-Bermúdez, F., Badsha, F., Kanton, S., Camp, J. G., Vernot, B., Köhler, K., & Lachmann, R. (2016). Differences and similarities between human and chimpanzee neural progenitors during cerebral cortex development. Elife , 5 , e18683.
The article analyzes cerebral organoids of human and chimpanzees using immunohistofluorescence, live imaging and single-cell transcriptomics. The researchers obtained human fetal brain tissue (11-13 weeks post conception after seeking maternal consent, which was dissected at room temperature. The authors find that the cytoarchitecture, cell type composition, and neurogenic gene expression programs of humans and chimpanzees are significantly similar. The imaging of the apical progenitor mitosis shows a lengthening of the prometaphase-metaphase in humans in comparison to chimpanzees. The small differences in cortical progenitors may have implications on human neocortex evolution.
According to the authors, human neocortex expansion is responsible for the impressive human cognitive abilities in comparison to the chimpanzees. The human brain is three times bigger in comparison to that of the chimpanzee. Also, the cerebral cortex in human beings contains twice as many cells, and it is responsible for memory, attention, awareness and thought. The authors claim that neocortex expansion is responsible for the differences. Neocortex expansion involves the increase in the number of cortical neurons developed during fetal development stages. The phenomenon is a reflection of a more significant and prolonged proliferative capacity of the human neural stem. The article is comprehensive, and it explores the differences between chimpanzee and human brain in detail.
Kwong, M., & Pemberton, T. J. (2014). Sequence differences at orthologous microsatellites inflate estimates of human-chimpanzee differentiation. BMC genomics , 15 (1), 990.
In the article, Kwong & Pemberton (2014) investigate the extent of sequence differences in human and chimpanzee orthologs. They identify the genomic targets of the primer pairs used to amplify 246 human derived autosomal microsatellites and calibrate PCR fragment lengths against reference sequences. The authors analyzed a dataset of the MS5879 subset of the Pemberton et al. [66] combined human-chimpanzee dataset that contains genotypes at 246 autosomal microsatellites in 5,795 individuals from 267 worldwide human populations and 84 individuals from six chimpanzee groups. Microsatellites are made up of short arrays of tandemly occurring repeats (STR) that vary in length. They have an abundance of different genomes; approximately 26-30 are among the fastest growing DNA sequences with high mutation rates. Consequently, they provide great information in studies on human and chimpanzee evolutionary history.
The results of the study show that human-chimpanzee differences within the embedded STR regions are frequent. The results of the study challenge prior interspecies comparisons using PCR fragment length genotypes from the standard set of DNA primer pairs. The results of the previous studies should be interpreted with caution as the implications of non-STR length differences remain unknown. The article is an excellent resource on the genetic differences between humans and chimpanzees.
Macfarlane, C. M., & Badge, R. M. (2015). Genome-wide amplification of proviral sequences reveals new polymorphic HERV-K (HML-2) proviruses in humans and chimpanzees that are absent from genome assemblies. Retrovirology , 12 (1), 35.
The study aimed to address the problem of a limited number of complete genomes affecting the human population census of proviruses of Betaretrovirus. Macfarlane & Badge (2015) proposed a suppression PCR-based method called genome-wide amplification of proviral sequences (GAPS) to selectively amplify DNA fragments containing the termini of HERV-K (HML-2) proviral sequences. Thus, the researchers analyze HERV-K (HML-2) proviral content of 101 humans and four common chimpanzees. The process isolates HERV-K (HML-2) proviruses that integrated into the genomes of the great apes after their divergence. The authors found out that detected a new insertionally polymorphic Type I HERV-K (HML-2) provirus. They also observed provirus versus solo long terminal repeat (LTR) polymorphism within humans at a previously unreported, but ancient, locus.
The study applied GAPS to 145 human and four chimpanzee DNA samples leading to the identification of fifteen HERV-K (HML-2) proviruses, ten human specific, two chimpanzees specific and three shared between the two species. The fact that humans and chimpanzees have three shared proviruses show that they have similarities, but they still have significant differences as reflected in the findings. The study contributes to the existing research on the differences between human beings and chimpanzees. HERV-K (HML-2) was first integrated into germline millions of years ago after the divergence from New World primates.
Fukuda, K., Ichiyanagi, K., Yamada, Y., Go, Y., Udono, T., Wada, S., & Sasaki, H. (2013). Regional DNA methylation differences between humans and chimpanzees are associated with genetic changes, transcriptional divergence and disease genes. Journal of human genetics , 58 (7), 446.
Fukuda and his colleagues explored the genetic differences between human beings and chimpanzees. The study is founded on the existing literature on the difference in genomic sequence and phenotypic differences between humans and chimpanzees. According to Fukuda et al. (2013), the epigenetic differences are not fully characterized. In the study, the researchers performed methylated DNA immunoprecipitation followed by tiling array hybridization (MeDIP-chip) to measure the entire lengths of chromosomes 21 and 22 for regional methylation differences between humans and chimpanzees. Chromosomes 21 and 22 are small in size and have high-density tiling microarray. The analysis of the peripheral blood leukocytes (PBLs) found 16 genomic regions showing methylation on chromosomes 21 and 22. The regional methylation differences are associated with genes implicated in diseases such as Alzheimer’s, diabetes mellitus or cancer. The researchers conclude that DNA methylation changes caused by small sequence changes contributed to the transcriptional and phenotypic diversification in hominid evolution. The article is educational, and it shows that small differences in the genetic sequence are responsible for the many differences between humans and chimpanzees.
Vermunt, M. W., Tan, S. C., Castelijns, B., Geeven, G., Reinink, P., De Bruijn, E., & Cuppen, E. (2016). Epigenomic annotation of gene regulatory alterations during evolution of the primate brain. Nature neuroscience , 19 (3), 494.
According to Vermunt et al. (2016) genome sequencing has discovered the many noncoding alterations between primate species. The differences include gene copy number variations, insertions, and deletions. But, they are yet to identify which of those genomes are regulatory and potentially relevant to the evolution of the human brain. Therefore, the authors annotated cis-regulatory elements (CREs) in humans and chimpanzee genomes. They apply chromatin immunoprecipitation followed by sequencing in different regions of the human brain. The researchers found that the overall positioning conservation of CREs is high, but with different usage. They also observed that the regulatory changes occurred before the divergence of human and chimpanzee. Only modest forms of regulatory elements are specific to humans.
The article adds to the existing literature on regulatory changes between human beings and chimpanzees before and after separation. The results of the study build on previous predictions and hypotheses on the effects of genomic differences between primate species and the relevant improvements to the human brain.
References
Fukuda, K., Ichiyanagi, K., Yamada, Y., Go, Y., Udono, T., Wada, S., & Sasaki, H. (2013). Regional DNA methylation differences between humans and chimpanzees are associated with genetic changes, transcriptional divergence and disease genes. Journal of human genetics , 58 (7), 446.
Kwong, M., & Pemberton, T. J. (2014). Sequence differences at orthologous microsatellites inflate estimates of human-chimpanzee differentiation. BMC genomics , 15 (1), 990.
Macfarlane, C. M., & Badge, R. M. (2015). Genome-wide amplification of proviral sequences reveals new polymorphic HERV-K (HML-2) proviruses in humans and chimpanzees that are absent from genome assemblies. Retrovirology , 12 (1), 35.
Mora-Bermúdez, F., Badsha, F., Kanton, S., Camp, J. G., Vernot, B., Köhler, K., & Lachmann, R. (2016). Differences and similarities between human and chimpanzee neural progenitors during cerebral cortex development. Elife , 5 , e18683.
Vermunt, M. W., Tan, S. C., Castelijns, B., Geeven, G., Reinink, P., De Bruijn, E., & Cuppen, E. (2016). Epigenomic annotation of gene regulatory alterations during evolution of the primate brain. Nature neuroscience , 19 (3), 494.
