"In general, evolution depends on a special combination of circumstances: part genetics, part time, and part environment. In the case of human brain evolution, the main environmental influence was adaptation to a 'shore-based' diet, which provided the world's richest source of nutrition, as well as a sedentary lifestyle that promoted fat deposition. Such a diet included shellfish, fish, marsh plants, frogs, bird's eggs, etc. Humans and, and more importantly, hominid babies started to get fat, a crucial distinction that led to the development of larger brains and to the evolution of modern humans. A larger brain is expensive to maintain and this increasing demand for energy results in, succinctly, survival of the fattest."
Robert P. Heaney is John A. Creighton University Professor, Creighton University, Omaha, Nebraska, United States.
Hominid evolution took place in an environment (equatorial East Africa) that provided a superabundance of both calcium and vitamin D, the first in available foods and the second through conversion of 7-dehydrocholesterol to pre-vitamin D in the skin, a reaction catalysed by the intense solar ultraviolet (UV) radiation. Seemingly as a consequence, the evolving human physiology incorporated provisions to prevent the potential of toxic excesses of both nutrients. For vitamin D the protection was of two sorts: skin pigmentation absorbed the critical UV wavelengths and thereby limited dermal synthesis of cholecalciferol; and slow delivery of vitamin D from the skin into the bloodstream left surplus vitamin in the skin, where continuing sun exposure led to its photolytic degradation to inert compounds. For calcium, the adaptation consisted of very inefficient calcium absorption, together with poor to absent systemic conservation. The latter is reflected in unregulated dermal calcium losses, a high sensitivity of renal obligatory calcium loss to other nutrients in the diet and relatively high quantities of calcium in the digestive secretions.
Today, chimpanzees in the original hominid habitat have diets with calcium nutrient densities in the range of 2 to 2.5 mmol per 100 kcal, and hunter-gatherer humans in Africa, South America and New Guinea still have diets very nearly as high in calcium (1.75 to 2 mmol per 100 kcal) (Eaton and Nelson, 1991). With energy expenditure of 3 000 kcal per day (a fairly conservative estimate for a contemporary human doing physical work), such diets would provide substantially in excess of 50 mmol of calcium per day. By contrast, median intake in women in North America and in many European countries today is under 15 mmol per day.
Two factors altered the primitive situation: the migration of humans from Africa to higher latitudes and the adoption of agriculture. The first red
A new study has concluded that one key part of the immune system, the ability of vitamin D to regulate anti-bactericidal proteins, is so important that is has been conserved through almost 60 million years of evolution and is shared only by primates, including humans - but no other known animal species.
Conclusion
We demonstrated that the VDRE in the CAMP gene originated from the exaptation of an AluSx SINE in the lineage leading to humans, apes, OWMs and NWMs and remained under purifying selection for the last 55–60 million years. We present convincing evidence of an evolutionarily fixed, Alu-mediated divergence in steroid hormone nuclear receptor gene regulation between humans/primates and other mammals. Evolutionary selection to place the primate CAMP gene under regulation of the vitamin D pathway potentiates the innate immune response and may counter the anti-inflammatory properties of vitamin D.
Exaptation of an ancient Alu short interspersed element provides a highly conserved vitamin D-mediated innate immune response in humans and primates.
Gombart AF, Saito T, Koeffler HP.
BMC Genomics. 2009 Jul 16;10:321.
PMID: 19607716
doi:10.1186/1471-2164-10-321
The timeline of human evolution outlines the major events in the development of human species, and the evolution of humans' ancestors. It includes a brief explanation of some animals, species or genera, which are possible ancestors of Homo sapiens sapiens. It begins with the origin of life and presents a possible line of descendants that led to humans. This timeline is based on studies from paleontology, developmental biology, morphology and from anatomical and genetic data. The study of human evolution is a major component of anthropology.
This timeline of the evolution of life outlines the major events in the development of life on the planet Earth (See Organism). For a thorough explanatory context, see the history of Earth, and geologic time scale. The dates given in this article are estimates based on scientific evidence.
In biology, evolution is the process by which populations of organisms acquire and pass on novel traits from generation to generation. Its occurrence over large stretches of time explains the origin of new species and ultimately the vast diversity of the biological world. Contemporary species are related to each other through common descent, products of evolution and speciation over billions of years.
To scroll left and right along the timeline, hover your mouse over the left or right areas. Centring the mouse pointer will stop the timeline from moving. Click on any of the date points to find out more about them.
Evolution is the unifying force in modern biology, but it remains a source of misunderstanding and controversy. Start finding out why it is so important with our beginner's guide
There are all sorts of ways to reconstruct the history of life on Earth. Pinning down when specific events occurred is often tricky, though. For this, biologists depend mainly on dating the rocks in which fossils are found, and by looking at the "molecular clocks" in the DNA of living organisms.
There are problems with each of these methods. The fossil record is like a movie with most of the frames cut out. Because it is so incomplete, it can be difficult to establish exactly when particular evolutionary changes happened
Espanjalaiset arkeologit ovat löytäneet 530 000 vuotta vanhan kallon, joka kuului vähintään viisivuotiaalle vammaiselle lapselle. Löytö muuttaa perinteisiä käsityksiä, joiden mukaan varhaiset ihmiset olisivat tappaneet epämuodostuneet yksilöt.
Lapsi kärsi harvinaisesta geneettisestä sairaudesta, jonka seurauksena kallon saumat luutuvat liian aikaisin. Tämä johtaa kallonsisäisen paineen kasvuun, minkä vuoksi lapsi jää vaikeasti vammaiseksi. Tutkijoiden mukaan lapsen selviäminen edes viiden vuoden ikään olisi vaatinut vanhemmiltaan tai yhteisöltään erityistä huolenpitoa.
Kallo löydettiin vuonna 2001 Espanjan Atapuercasta, ja sen uskotaan kuuluvan neandertalinihmisiä edeltäneelle Homo heidelbergensis -ihmiselle.
Reading the cracked brown fragments of fossils and sequences of DNA, scientists have found clues that the story of human origins has more convolutions than previously thought. The account of our shared human heritage now includes more controversial plot twists and mysteries. Was the remarkable seven-million-year-old skull found in July 2002 in Chad really one of our first forebears, or a distant dead-end cousin with precociously evolved features? Did modern humans really originate in Africa alone, as is widely held, or in multiple locales? Were Neandertals the crude, brutish cavemen of comic strips or did they have a refined, artistic culture? And of course, why didnt our kind perish with the rest of the hominids? Were we luckier, more lingual or just more lethal than the rest?